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                                                          - 527 -
                               Nebraska Supreme Court Advance Sheets
                                        305 Nebraska Reports
                                                 STATE v. SCHROEDER
                                                   Cite as 305 Neb. 527




                                         State of Nebraska, appellee, v.
                                        Patrick W. Schroeder, appellant.
                                                     ___ N.W.2d ___

                                           Filed April 17, 2020.    No. S-18-582.

                 1. Sentences: Death Penalty: Appeal and Error. In a capital sentenc-
                    ing proceeding, the Nebraska Supreme Court conducts an independent
                    review of the record to determine if the evidence is sufficient to support
                    imposition of the death penalty.
                 2. Sentences: Aggravating and Mitigating Circumstances: Appeal and
                    Error. When reviewing the sufficiency of the evidence to sustain the
                    trier of fact’s finding of an aggravating circumstance, the relevant ques-
                    tion for the Nebraska Supreme Court is whether, after viewing the evi-
                    dence in the light most favorable to the State, any rational trier of fact
                    could have found the essential elements of the aggravating circumstance
                    beyond a reasonable doubt.
                 3. ____: ____: ____. A sentencing panel’s determination of the existence
                    or nonexistence of a mitigating circumstance is subject to de novo
                    review by the Nebraska Supreme Court.
                 4. Sentences: Death Penalty: Aggravating and Mitigating Circum­
                    stances: Appeal and Error. In reviewing a sentence of death, the
                    Nebraska Supreme Court conducts a de novo review of the record to
                    determine whether the aggravating and mitigating circumstances support
                    the imposition of the death penalty.
                 5. Rules of Evidence. In proceedings where the Nebraska Evidence Rules
                    apply, the admissibility of evidence is controlled by the Nebraska
                    Evidence Rules; judicial discretion is involved only when the rules make
                    discretion a factor in determining admissibility.
                 6. Constitutional Law: Statutes: Appeal and Error. The constitutionality
                    of a statute presents a question of law, which an appellate court indepen-
                    dently reviews.
                 7. Sentences: Death Penalty: Homicide: Aggravating and Mitigating
                    Circumstances: Appeal and Error. Under Nebraska law, the death
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            Nebraska Supreme Court Advance Sheets
                     305 Nebraska Reports
                            STATE v. SCHROEDER
                              Cite as 305 Neb. 527

      penalty is imposed for a conviction of murder in the first degree only in
      those instances when the aggravating circumstances existing in connec-
      tion with the crime outweigh the mitigating circumstances.
 8.   Trial: Rebuttal Evidence. Rebuttal evidence is confined to new mat-
      ters first introduced by the opposing party and limited to that which
      explains, disproves, or counteracts the opposing party’s evidence.
 9.   Sentences: Death Penalty: Aggravating and Mitigating Circum­
      stances: Evidence. In a death penalty case, a sentencing panel has the
      discretion to hear evidence to address potential mitigating circumstances
      regardless of whether the defendant presents evidence on that issue.
10.   Sentences: Evidence. A sentencing court has broad discretion as to
      the source and type of evidence and information which may be used
      in determining the kind and extent of the punishment to be imposed,
      and evidence may be presented as to any matter that the court deems
      relevant to the sentence.
11.   Sentences: Death Penalty: Aggravating and Mitigating Circum­
      stances: Evidence. In a death penalty case, a sentencing panel may
      permit the State to present evidence to contradict potential mitigators
      even though a defendant failed to present affirmative evidence.
12.   Sentences: Death Penalty: Homicide. A sentencing order in a death
      penalty case must specify the factors the sentencing panel relied upon in
      reaching its decision and focus on the individual circumstances of each
      homicide and each defendant.
13.   Constitutional Law: Sentences: Death Penalty: Aggravating and
      Mitigating Circumstances. The U.S. Constitution does not require the
      sentencing judge or judges to make specific written findings in death
      penalty cases with regard to nonstatutory mitigating factors.
14.   Sentences: Aggravating and Mitigating Circumstances: Appeal and
      Error. The Nebraska Supreme Court will not fault a sentencing panel
      for failing to discuss a nonstatutory mitigating circumstance that it was
      not specifically asked to consider.
15.   Death Penalty: Aggravating and Mitigating Circumstances. During
      the consideration of statutory mitigating factors in a death penalty case,
      the mere identification of a history of incarceration, without more,
      is insufficient to allege unusual pressures or influences or establish
      extreme mental or emotional disturbance.
16.   Sentences: Homicide: Aggravating and Mitigating Circumstances:
      Judgments: Juries: Presentence Reports. When an offender has been
      convicted of first degree murder and waives the right to a jury determi-
      nation of an alleged aggravating circumstance, the court must order a
      presentence investigation of the offender and the panel must consider a
      written report of such investigation in its sentencing determination.
                                    - 529 -
           Nebraska Supreme Court Advance Sheets
                    305 Nebraska Reports
                           STATE v. SCHROEDER
                             Cite as 305 Neb. 527

17. Presentence Reports. A presentence investigation and report shall
    include, when available, any submitted victim statements and an analy-
    sis of the circumstances attending the commission of the crime and the
    offender’s history of delinquency or criminality, physical and mental
    condition, family situation and background, economic status, education,
    occupation, and personal habits.
18. Presentence Reports: Probation and Parole. A presentence investiga-
    tion and report may include any matters the probation officer deems
    relevant or the court directs to be included.
19. Constitutional Law: Criminal Law: Sentences: Right to Counsel. An
    accused has a state and federal constitutional right to be represented by
    an attorney in all critical stages of a criminal prosecution which can lead
    to a sentence of confinement.
20. Right to Counsel: Waiver. A defendant may waive the right to counsel
    so long as the waiver is made knowingly, voluntarily, and intelligently.
21. Constitutional Law: Right to Counsel. The same constitutional provi-
    sions that provide a defendant the right to counsel also guarantee the
    right of the accused to represent himself or herself.
22. Attorney and Client. The right to self-representation plainly encom-
    passes certain specific rights of the defendant to have his voice heard,
    including that the pro se defendant must be allowed to control the orga-
    nization and content of his own defense.
23. Sentences: Death Penalty: Attorney and Client: Aggravating and
    Mitigating Circumstances: Evidence: Waiver. Control of the orga-
    nization and content of a defense may include a waiver of the right to
    pre­sent mitigating evidence during sentencing in a death penalty case.
24. Criminal Law: Sentences: Death Penalty: Appeal and Error. Because
    a death sentence is different from any other criminal penalty and no sys-
    tem based on human judgment is infallible, the Nebraska Supreme Court
    has taken, and should continue to take, the extra step to ensure fairness
    and accuracy with the imposition of the death penalty.
25. Criminal Law: Statutes. Penal statutes are to be strictly construed in
    favor of the defendant.
26. Sentences: Evidence: Presentence Reports. Even if the State presents
    evidence in favor of a specific sentence and the defendant declines to
    present contrary evidence, a court receives and must consider indepen-
    dent information from a presentence investigation report.
27. Sentences: Death Penalty: Evidence: Presentence Reports. In a death
    penalty case, a sentencing panel is required to review a presentence
    investigation report and determine whether it contradicts the State’s evi-
    dence of aggravating factors and whether any mitigating circumstances
    exist, including specifically delineated statutory mitigators.
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           Nebraska Supreme Court Advance Sheets
                    305 Nebraska Reports
                           STATE v. SCHROEDER
                             Cite as 305 Neb. 527

28. Death Penalty: Aggravating and Mitigating Circumstances: Proof.
    While the State must prove aggravating circumstances beyond a rea-
    sonable doubt in a death penalty case, there is no burden of proof with
    regard to mitigating circumstances.
29. Sentences: Death Penalty: Aggravating and Mitigating Circum­
    stances: Judgments. Once a sentencing panel in a death penalty case
    makes its determinations about the existence of aggravating and mitigat-
    ing circumstances, the panel is then required to undertake a proportion-
    ality review.
30. Criminal Law: Sentences: Death Penalty: Words and Phrases. A pro-
    portionality review in a death penalty case looks at whether the sentence
    of death is excessive or disproportionate to the penalty imposed in simi-
    lar cases, considering both the crime and the defendant. Proportionality
    review is not constitutionally mandated.
31. Sentences: Death Penalty: Statutes: Appeal and Error. The propor-
    tionality review in a death penalty case exists in Nebraska by virtue of
    statutes which direct the Nebraska Supreme Court to conduct a propor-
    tionality review in each appeal in which a death sentence is imposed.
32. Sentences: Death Penalty. A court’s proportionality review spans all
    previous cases in which a sentence of death is imposed and is not depen-
    dent on which cases are put forward by the parties.
33. Sentences: Death Penalty: Aggravating and Mitigating Circum­
    stances: Judgments: Juries. Even when a jury determines the existence
    of an aggravating circumstance, a sentencing panel is required to put in
    writing its consideration of whether the determined aggravating circum-
    stance justifies the imposition of a sentence of death, whether mitigating
    circumstances exist, and whether a sentence of death would be excessive
    or disproportionate to penalties imposed in similar cases.
34. ____: ____: ____: ____: ____. A sentencing panel’s order imposing
    a sentence of death where a jury has determined the existence of an
    aggravating circumstance must specifically refer to the aggravating and
    mitigating circumstances weighed in the determination of the panel.
35. Sentences: Death Penalty: Statutes. Nebraska’s capital sentencing
    scheme provides additional statutory steps and considerations to ensure
    fairness and accuracy, and these safeguards exist regardless of a defend­
    ant’s strategy at the penalty phase.
36. Sentences: Death Penalty. Due to Nebraska’s statutory capital sentenc-
    ing scheme, a defendant cannot “choose” the death penalty.
37. Courts: Sentences: Death Penalty. A sentencing decision in a death
    penalty case rests with the court alone.
38. Sentences: Death Penalty: Aggravating and Mitigating Circum­
    stances: Evidence: Presentence Reports. In order to sentence a
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            Nebraska Supreme Court Advance Sheets
                     305 Nebraska Reports
                            STATE v. SCHROEDER
                              Cite as 305 Neb. 527

      defendant to death, the statutory scheme requires that a sentencing
      panel consider not only evidence and argument presented by the parties
      but also an independently compiled presentence investigation report to
      determine whether the alleged aggravating circumstance exists, deter-
      mine whether any mitigating factors are present which would weigh
      against the imposition of the death penalty, and conduct a proportional-
      ity review weighing the aggravating and mitigating factors and compar-
      ing the facts to previous cases where the death penalty was imposed.
39.   Trial: Parties. A defendant is entitled to present a defense and is guar-
      anteed the right to choose the objectives for that defense.
40.   Attorney and Client. A self-represented defendant must be allowed to
      control the organization and content of his own defense.
41.   Constitutional Law: Right to Counsel: Sentences: Aggravating
      and Mitigating Circumstances: Evidence: Waiver. When a defend­
      ant waives counsel and the presentation of mitigating evidence, the
      appointment of an advocate to present evidence and argue against the
      imposition of a sentence overrides that defendant’s constitutional right
      to control the organization and content of his or her own defense dur-
      ing sentencing.
42.   Right to Counsel: Waiver. A criminal defendant has the right to waive
      counsel and present his or her own defense.
43.   Sentences: Death Penalty: Right to Counsel: Evidence: Waiver. In a
      death penalty case, a defendant’s right to waive counsel and present his
      or her own defense includes the right of the defendant to elect not to
      present additional evidence or argument during the penalty proceedings.
44.   Sentences: Death Penalty: Aggravating and Mitigating Circum­
      stances: Appeal and Error. In reviewing a sentence of death, the
      Nebraska Supreme Court conducts a de novo review of the record to
      determine whether the aggravating and mitigating circumstances support
      the imposition of the death penalty.
45.   ____: ____: ____: ____. In reviewing a sentence of death, the Nebraska
      Supreme Court considers whether the aggravating circumstances justify
      imposition of a sentence of death and whether any mitigating circum-
      stances found to exist approach or exceed the weight given to the aggra-
      vating circumstances.
46.   ____: ____: ____: ____. The Nebraska Supreme Court is required, upon
      appeal, to determine the propriety of a death sentence by conducting a
      proportionality review, comparing the aggravating and mitigating cir-
      cumstances with those present in other cases in which a court imposed
      the death penalty.
47.   Sentences: Death Penalty. The purpose of a proportionality review in a
      death penalty case is to ensure that the sentences imposed in a case are
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            Nebraska Supreme Court Advance Sheets
                     305 Nebraska Reports
                            STATE v. SCHROEDER
                              Cite as 305 Neb. 527

      no greater than those imposed in other cases with the same or similar
      circumstances.
48.   Sentences: Death Penalty: Aggravating and Mitigating Circum­
      stances: Appeal and Error. The Nebraska Supreme Court’s propor-
      tionality review looks only to other cases in which the death penalty
      has been imposed and requires the court to compare the aggravating
      and mitigating circumstances of the case on appeal with those present in
      those other cases.
49.   Death Penalty. A proportionality review in a death penalty case does
      not require that a court “color match” cases precisely.
50.   Sentences: Death Penalty. The question when conducting a propor-
      tionality review in a death penalty case is simply whether the cases
      being compared are sufficiently similar, considering both the crime and
      the defendant, to provide the court with a useful frame of reference for
      evaluating the sentence in the instant case.
51.   Sentences: Death Penalty: Aggravating and Mitigating Circum­
      stances. One aggravating circumstance may be sufficient under
      Nebraska’s statutory system for the imposition of the death penalty.
52.   ____: ____: ____. In a proportionality review, the evaluation of whether
      the death penalty should be imposed in a specific case is not a mere
      counting process of “X” number of aggravating circumstances and
      “Y” number of mitigating circumstances and, instead, asks whether the
      reviewed cases are sufficiently similar to provide a useful reference for
      that evaluation.

   Appeal from the District Court for Johnson County: Vicky
L. Johnson, Judge. Affirmed.
  Sarah P. Newell, of Nebraska Commission on Public
Advocacy, for appellant.
  Douglas J. Peterson, Attorney General, and James D. Smith,
Solicitor General, for appellee.
  Christopher L. Eickholt, of Eickholt Law, L.L.C., Cassandra
Stubbs, of American Civil Liberties Union Foundation, and
Amy A. Miller, of ACLU of Nebraska Foundation, for amicus
curiae ACLU and ACLU of Nebraska.
  Heavican, C.J., Miller-Lerman, Cassel, Stacy, Funke,
and Papik, JJ., and Moore, Chief Judge.
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         Nebraska Supreme Court Advance Sheets
                  305 Nebraska Reports
                      STATE v. SCHROEDER
                        Cite as 305 Neb. 527

   Funke, J.
   Patrick W. Schroeder appeals his sentence of death for
first degree murder of Terry Berry, Jr. This is a mandatory
direct appeal pursuant to Neb. Rev. Stat. § 29-2525 (Cum.
Supp. 2018) and article I, § 23, of the Nebraska Constitution.
Schroeder waived counsel, pled guilty without a plea agree-
ment, waived the right to a jury on the issue of aggravating
factors, declined to present evidence of aggravating or mitigat-
ing factors, and declined to cooperate for the preparation of the
presentence investigation report.
   On appeal, Schroeder was appointed counsel and now con-
tends that the sentencing panel erred in allowing the State to
introduce evidence to refute unpresented mitigating evidence,
failing to consider and weigh mitigating evidence from the
presentence investigation report, failing to request documenta-
tion from the Department of Correctional Services (DCS) of
Schroeder’s time in custody for mitigation purposes, sentenc-
ing Schroeder to death with insufficient safeguards to prevent
arbitrary results, and finding Schroeder should be sentenced to
death after balancing the aggravating evidence and mitigating
evidence. For the reasons set forth herein, we affirm.
                       BACKGROUND
                    Factual Background
   At the time of the events leading to Schroeder’s instant
conviction, Schroeder was incarcerated at Tecumseh State
Correctional Institution (TSCI). This incarceration was pur-
suant to a 2007 conviction for the first degree murder of
Kenneth Albers in which Schroeder was sentenced to life
imprisonment.
   In March 2017, while housed in a cell intended for one
occupant, Schroeder was asked if he would consider a room-
mate due to overcrowding. Schroeder agreed but wanted a
roommate with whom he was compatible. Prison officials
assigned Berry to Schroeder’s cell. Schroeder did not consider
Berry to be compatible with him and told prison officials that
he did not want Berry as a cellmate. Schroeder did not know
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         Nebraska Supreme Court Advance Sheets
                  305 Nebraska Reports
                      STATE v. SCHROEDER
                        Cite as 305 Neb. 527

Berry personally before the assignment but knew of Berry as
“‘a loudmouth, a punk.’” Berry was 22 years old and convicted
of second degree forgery and a confined person violation.
Berry was due for release approximately 2 weeks after his
assignment to Schroeder’s cell.
   Schroeder had described Berry as a constant talker with
extremely poor hygiene. During their shared confinement,
Schroeder would urge Berry to be quieter and clean up after
himself. Schroeder alleged that he had told prison staff that
placing Berry with him would be an unworkable, bad arrange-
ment. Schroeder described that prison staff who came by his
cell would acknowledge the poor fit and even joke that it was
surprising Schroeder had not killed Berry yet. By April 13,
2017, Schroeder decided to himself that “‘[s]omething was
gonna happen’” if Berry was not moved.
   On April 15, 2017, Berry was watching “UFC” on televi-
sion in the cell and, as Schroeder explained, Berry “‘would
not shut up.’” Schroeder instructed Berry to move his chair
to face the television with his back to Schroeder. Schroeder
proceeded to put Berry in a chokehold and locked his hands.
He continued to choke Berry for about 5 minutes until his
arms got tired and then took a nearby towel, wrapped it around
Berry’s neck, and continued to choke him for about 5 more
minutes. At that point, Schroeder let up on the towel, believ-
ing Berry was dead. Schroeder claimed he then tried to push
the call button in his cell to alert staff to Berry’s condition.
Around 30 minutes later, Schroeder alerted a passing guard
that Berry was on the floor by asking, “‘How do you deal
with a dead body in a cell?’” The guard believed Schroeder
was joking until Schroeder picked up and dropped Berry’s
leg. Schroeder has stated that he summoned the guard not for
Berry’s benefit, but because he wanted Berry’s body removed
from the cell.
   Berry was transported to a medical facility. On April 19,
2017, Berry died, having been declared brain dead. A search
of the cell revealed a torn “kite,” a form inmates use to com-
municate with prison staff, dated April 13, 2017, and located in
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            Nebraska Supreme Court Advance Sheets
                     305 Nebraska Reports
                           STATE v. SCHROEDER
                             Cite as 305 Neb. 527

the trash. The discarded kite stated that prison staff had to get
Berry out of the cell before he got hurt.

                   Procedural Background
   Pursuant to these events, Schroeder was charged in April
2017 with first degree murder and use of a weapon to commit
a felony. Within an information filed in June, the State submit-
ted a notice of aggravation alleging Schroeder had been con-
victed of another murder, been convicted of a crime involving
the use or threat of violence to the person, or had a substantial
prior history of serious assaultive or terrorizing criminal activ­
ity. 1 Schroeder was appointed counsel and entered a plea of
not guilty.
   A hearing was held following Schroeder’s subsequent
request to dismiss counsel and represent himself. The court
granted Schroeder’s motion and discharged his counsel but
also appointed that same counsel to act in a standby role.
Representing himself, Schroeder withdrew a pending motion
to quash and requested leave to withdraw his prior plea of not
guilty. The court granted Schroeder leave to withdraw his prior
plea and rearraigned him. Thereafter, Schroeder pled guilty to
both counts and the court found him guilty of those charges
beyond a reasonable doubt.

             Presentence Investigation Report
   The court ordered a presentence investigation report.
Schroeder declined to answer questions or participate in its
preparation. However, the current report did attach the 2007
presentence investigation report from Schroeder’s earlier con-
victions, which supplies more background information.
   According to the report, Schroeder was born in June 1977.
Schroeder’s biological father abandoned his family when
Schroeder was an infant. Schroeder’s mother and stepfather
raised him in his early years. Schroeder described his step­father
as an alcoholic. Schroeder’s mother and stepfather separated
1
    See Neb. Rev. Stat. § 29-2523(1)(a) (Cum. Supp. 2018).
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         Nebraska Supreme Court Advance Sheets
                  305 Nebraska Reports
                      STATE v. SCHROEDER
                        Cite as 305 Neb. 527

when Schroeder was 9 years old, and Schroeder moved with
his mother to Kearney, Nebraska. Schroeder has not had con-
tact with his stepfather since he was 12 years old. Schroeder
has two older brothers but, at the time of the 2007 report, was
not close to either of them. While Schroeder’s biological father
did take him in for a brief period of time when he was 12 years
old, Schroeder was removed and sent to a juvenile facility
because his father caught him smoking marijuana. Schroeder
denied being abused or neglected and described his childhood
as “‘typical.’” Schroeder has a history of “placement in foster
care and group home situations including a number of run-
aways.” At one point as a teenager, Schroeder was placed with
his grandparents for a period of time.
   Schroeder was married in 1998 and has one child from that
marriage, but the couple has since divorced. At the time of the
2007 report, Schroeder described that the child was adopted
by his ex-wife’s present husband and that Schroeder has no
contact with the child. Schroeder remarried in 2003, and his
wife had three children from prior relationships. However,
Schroeder said in the 2007 report that while the couple was
then together, he expected the situation to change under the
circumstances.
   The presentence investigation report provides that Schroeder
has an eighth grade education. Before he was incarcerated in
2007, he had been employed in various farmwork and con-
struction jobs.
   Schroeder reported that he first used alcohol when he was 13
years old and that he experimented with marijuana and cocaine
when he was 15 years old. Schroeder also admitted he had
used methamphetamine on a daily basis for approximately 3 to
4 months, with the last use in 2003. While Schroeder denied
receiving treatment, previous prison records indicated he was
placed in substance abuse programming in 1991. Schroeder
asserted that from April 2005 until his 2006 arrest, he was
“‘hooked on opiates’” and was taking between 500 and 800
pills per month, some of which were prescribed and some of
which were not.
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         Nebraska Supreme Court Advance Sheets
                  305 Nebraska Reports
                      STATE v. SCHROEDER
                        Cite as 305 Neb. 527

   The report explained that in 1985, Schroeder was first
charged with criminal mischief in juvenile court when he was
12 years old. Between 1987 and 1992, Schroeder was also
charged in juvenile court with aiding and abetting, escape,
theft, minor in possession of alcohol, and theft by exercis-
ing control. He was ordered to serve probation as well as
being placed in the Youth Rehabilitation and Treatment Center
in Kearney.
   Since reaching the age of majority, in addition to his 2007
convictions, Schroeder has been convicted of bank robbery,
forgery, escape, theft, assault, driving under suspension, con-
tributing to the delinquency of a child, driving under the
influence, and issuing bad checks. He has been sentenced to
multiple terms of incarceration and terms of supervision. He
has had two of his terms of probation revoked and completed
others unsatisfactorily.
                  Sentencing Proceedings
   A scheduling hearing was held in August 2017. Schroeder
waived his right to a jury for a determination of the aggrava-
tion allegation. The court accepted this waiver after making
inquiry and finding, beyond a reasonable doubt, that Schroeder
was competent and that his decision was made freely, volun-
tarily, knowingly, and intelligently. Thereafter, a three-judge
panel was convened for a sentencing hearing on Schroeder’s
first degree murder conviction.
   On the aggravation allegation, the State presented evidence
of Schroeder’s 2007 conviction for Albers’ murder. A ser-
geant with the Nebraska State Patrol testified that he was
the lead investigator for that case. His testimony and a video
of his interview with Schroeder described that Albers was a
75-year-old farmer who had previously employed Schroeder.
Believing Albers had several thousand dollars in cash at his
residence, Schroeder had driven to Albers’ house, rung the
doorbell, entered the home, and awakened Albers. Schroeder
demanded money, threatened Albers, and hit him in the head
with a nightstick. Albers recognized Schroeder during this
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         Nebraska Supreme Court Advance Sheets
                  305 Nebraska Reports
                      STATE v. SCHROEDER
                        Cite as 305 Neb. 527

exchange and called him by name. Schroeder forced Albers
to open a lockbox in which Schroeder believed the cash was
kept, after which Schroeder took Albers outside to an adjacent
shop. At the shop, Albers turned toward Schroeder, attempting
to defend himself. Schroeder struck Albers with the nightstick
four or five times. With Albers on the floor, Schroeder dragged
him out of the shop, tied him up with battery cables, and
placed him in the back of Albers’ pickup. Schroeder then drove
Albers, who was still alive, to an abandoned well on the prop-
erty and dumped him into it. Schroeder explained to the ser-
geant that he had made the decision to kill Albers a few days
before the robbery. The doctor who performed the autopsy on
Albers testified that the cause of Albers’ death was blunt force
trauma to his head.
   Schroeder declined to cross-examine the State’s witnesses,
present rebuttal evidence, or argue against the State’s claim on
the aggravation allegation.
   As to mitigating factors, Schroeder again declined to pre­
sent any evidence or argument. However, the State requested,
and the court granted, permission to present evidence to negate
possible statutory mitigating circumstances. Here, the State
presented evidence related to Berry’s murder. Investigator
Stacie Lundgren of the Nebraska State Patrol testified to her
interview with Schroeder where he described how and why
he killed Berry. This interview was also described in the pre-
sentence investigation report. The doctor who performed the
autopsy of Berry opined that the cause of death was compres-
sional asphyxia, a form of strangulation where the structures
of the neck are compressed. Cpl. Steve Wilder explained that
he was the correctional officer whom Schroeder flagged down
to remove Berry after Schroeder had choked him. Cpl. Joseph
Eppens testified he had moved Schroeder from his cell follow-
ing the incident. Eppens explained that Schroeder told him he
had previously informed correctional staff he did not want a
cellmate and that he joked, “[T]his is what happens when we
watch UFC.” Finally, a TSCI employee testified that he had
notarized a writing in which Schroeder stated:
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         Nebraska Supreme Court Advance Sheets
                  305 Nebraska Reports
                      STATE v. SCHROEDER
                        Cite as 305 Neb. 527

         My name is Patrick Schroeder. I’m 40 years old and
      I killed Terry Berry on April 15[,] 2017[.] I killed Berry
      because I wanted to, I knew I was going to kill him the
      moment staff put him in my cell on April 10[,] 2017. . . .
         I’m writing this statement to inform the court that if
      given another life term I will kill again and we will be
      right back in court doing this all over again.
   The court allowed the parties to make arguments. Schroeder
declined. On the aggravation allegation, the State noted that
it provided a certified copy of Schroeder’s previous murder
conviction and testimony concerning the events leading to that
conviction. As to mitigating circumstances, the State stated,
in part:
      [T]he State has offered evidence considering the statutory
      mitigating circumstances, and the purpose of the evidence
      was to affirmatively show that there were no statutory
      mitigators that exist in this case.
         The circumstances to be considered for mitigation
      include whether or not the defendant acted under unusual
      pressure or influence. I want to emphasize the word
      “unusual.” His justification[s] for his actions are more of
      a nuisance than they are unusual pressure.
         It was displeasure or disagreement with a roommate
      and how the roommate either talked too much or his
      hygiene wasn’t appropriate for . . . Schroeder’s standards,
      and I don’t think that constitutes unusual pressure or
      influence.
         He’s not under the . . . dominion of another. . . .
      Schroeder acted by himself, and I would say he probably
      was the boss in the cell.
         There is no undue influence of extreme mental or emo-
      tional disturbance. . . . Schroeder was clear thinking, and
      by the evidence that’s been presented, his thought process
      started almost immediately upon . . . Berry becoming
      his cellmate. And in his written statement, that is really
      clear. And even in his interview with the investigator, he
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         Nebraska Supreme Court Advance Sheets
                  305 Nebraska Reports
                      STATE v. SCHROEDER
                        Cite as 305 Neb. 527

     started thinking about this several days before it actu-
     ally happened.
        So he wasn’t under any influence of extreme mental or
     emotional disturbance. This was a thought process delib-
     erate and pretty cold blooded.
        ....
        The evidence shows that he was the sole person com-
     mitting this crime. There is no accomplice. And his par-
     ticipation is the . . . death-causing participation.
        The State would argue that . . . Berry’s habits as
     described by [Schroeder do] not make him a participant
     [in the incident].
        ....
        [Schroeder] was a prisoner at the institution. No evi-
     dence of impairment. The only evidence is that he’s clear-
     headed, he’s thinking, and he planned.

                       Order of Sentence
   In the panel’s order of sentence, the panel found the State
proved the aggravation allegation beyond a reasonable doubt,
citing Schroeder’s previous conviction and the testimony
describing the events leading to that conviction.
   The panel also addressed possible statutory mitigating cir-
cumstances, noting, “The State was allowed to present evi-
dence that is probative of the non-existence of statutory or non-
statutory mitigating circumstances, and did so[, and Schroeder]
was allowed to present evidence that is probative of the exis-
tence of a statutory or non-statutory mitigating circumstance[,
but] chose not to . . . .” After analyzing each of the mitigating
grounds defined by § 29-2523(2) and giving Schroeder the
benefit of all inferences, the panel did not find there were any
statutory mitigating circumstances.
   The panel addressed various nonstatutory mitigating factors.
The panel found two of these factors existed and weighed in
Schroeder’s favor, including that Schroeder’s guilty plea spared
Berry’s family the trauma of a trial and the State the expense of
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                       STATE v. SCHROEDER
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a trial and that Schroeder’s childhood and family were dysfunc-
tional. While finding three other factors did not exist, the panel
noted the following: Schroeder is not well educated, but there
is no evidence of a borderline intellect or diminished cogni-
tive ability and he clearly knows right from wrong; Schroeder
takes medication for depression, but there is nothing to suggest
that this depression contributed to his actions and there is no
evidence that his psychiatric or psychological history rises to
the level of a mitigating circumstance; and the record does not
suggest Schroeder has generally been a problem to officials
during his confinement, but this prior conduct does not rise to
the level of a mitigating factor. The panel acknowledged that
Schroeder apparently “expressly welcomes a death sentence”
but explained this was not considered and that “[i]t is the law,
and not [Schroeder’s] wishes, that compels this Panel’s ulti-
mate conclusion.”
   The panel concluded that the two nonstatutory mitigating
circumstances were given little weight because these two fac-
tors did not approach or exceed the weight given to the aggra-
vating circumstance. The panel then conducted a proportional-
ity review and found that a sentence of death is not excessive
or disproportionate to the penalty imposed in similar cases.
Based upon all of the above, the panel sentenced Schroeder
to death.
                 ASSIGNMENTS OF ERROR
   Schroeder assigns, restated, that the sentencing court erred
in (1) allowing the State to introduce evidence to rebut unpre-
sented mitigating evidence, (2) failing to consider and prop-
erly weigh mitigating evidence from the presentence inves-
tigation report, (3) failing to request DCS documentation of
Schroeder’s time in custody for mitigation purposes, (4) sen-
tencing Schroeder to death with insufficient safeguards to
prevent arbitrary results, and (5) sentencing Schroeder to death
after balancing the aggravating evidence and mitigating evi-
dence and conducting the proportionality review.
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                           STATE v. SCHROEDER
                             Cite as 305 Neb. 527

                    STANDARD OF REVIEW
   [1] In a capital sentencing proceeding, this court conducts an
independent review of the record to determine if the evidence
is sufficient to support imposition of the death penalty. 2
   [2-4] When reviewing the sufficiency of the evidence to
sustain the trier of fact’s finding of an aggravating circum-
stance, the relevant question for this court is whether, after
viewing the evidence in the light most favorable to the State,
any rational trier of fact could have found the essential ele-
ments of the aggravating circumstance beyond a reasonable
doubt. 3 The sentencing panel’s determination of the existence
or nonexistence of a mitigating circumstance is subject to de
novo review by this court. 4 In reviewing a sentence of death,
the Nebraska Supreme Court conducts a de novo review of the
record to determine whether the aggravating and mitigating
circumstances support the imposition of the death penalty. 5
   [5] In proceedings where the Nebraska Evidence Rules
apply, the admissibility of evidence is controlled by the
Nebraska Evidence Rules; judicial discretion is involved
only when the rules make discretion a factor in determining
admissibility. 6
   [6] The constitutionality of a statute presents a question of
law, which an appellate court independently reviews. 7
                        ANALYSIS
                 Rebuttal of Mitigating
                     Circumstances
   [7] Under Nebraska law, the death penalty is imposed
for a conviction of murder in the first degree only in those
2
    State v. Jenkins, 303 Neb. 676, 931 N.W.2d 851 (2019).
3
    State v. Torres, 283 Neb. 142, 812 N.W.2d 213 (2012).
4
    Jenkins, supra note 2.
5
    Id.
6
    Torres, supra note 3.
7
    Jenkins, supra note 2.
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                          STATE v. SCHROEDER
                            Cite as 305 Neb. 527

instances when the aggravating circumstances existing in
connection with the crime outweigh the mitigating circum­
stances. 8 When, as here, a defendant waives the right to a
jury determination of alleged aggravating circumstances, the
proc­ess for a sentencing panel to consider, find, and weigh the
applicable aggravating and mitigating circumstances is set out
by Neb. Rev. Stat. § 29-2521(2) (Cum. Supp. 2018). Section
29-2521(2) states:
      In the sentencing determination proceeding before a panel
      of judges when the right to a jury determination of the
      alleged aggravating circumstances has been waived, the
      panel shall . . . hold a hearing. At such hearing, evidence
      may be presented as to any matter that the presiding judge
      deems relevant to sentence and shall include matters
      relating to the aggravating circumstances alleged in the
      information, to any of the mitigating circumstances set
      forth in section 29-2523, and to sentence excessiveness
      or disproportionality. The Nebraska Evidence Rules shall
      apply to evidence relating to aggravating circumstances.
      Each aggravating circumstance shall be proved beyond a
      reasonable doubt. Any evidence at the sentencing deter-
      mination proceeding which the presiding judge deems to
      have probative value may be received. The state and the
      defendant or his or her counsel shall be permitted to pre­
      sent argument for or against sentence of death.
   The mitigating circumstances required to be considered
under § 29-2521 and set forth in § 29-2523(2) include:
         (a) The offender has no significant history of prior
      criminal activity;
         (b) The offender acted under unusual pressures or
      influences or under the domination of another person;
         (c) The crime was committed while the offender was
      under the influence of extreme mental or emotional
      disturbance;
         (d) The age of the defendant at the time of the crime;
8
    Neb. Rev. Stat. § 29-2519 (Cum. Supp. 2018).
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         (e) The offender was an accomplice in the crime com-
      mitted by another person and his or her participation was
      relatively minor;
         (f) The victim was a participant in the defendant’s con-
      duct or consented to the act; or
         (g) At the time of the crime, the capacity of the defend­
      ant to appreciate the wrongfulness of his or her conduct
      or to conform his or her conduct to the requirements of
      law was impaired as a result of mental illness, mental
      defect, or intoxication.
   [8] Schroeder initially claims that the sentencing panel erred
by allowing the State to present evidence to rebut the statutory
mitigating circumstances even though Schroeder did not offer
any evidence on mitigation. In making this claim, Schroeder
cites the proposition that rebuttal evidence is confined to new
matters first introduced by the opposing party and limited to
that which explains, disproves, or counteracts the opposing
party’s evidence. 9
   [9-11] Contrary to Schroeder’s assertions under this assign-
ment, a sentencing panel has the discretion to hear evidence
to address potential mitigating circumstances regardless of
whether the defendant presents evidence on that issue. As
quoted above, § 29-2521(2) allows a sentencing panel to
receive “[a]ny evidence” at the sentencing proceeding which
the presiding judge deems to have probative value relevant
to the sentence including to any of the statutory mitigating
circumstances. 10 A sentencing court has broad discretion as to
the source and type of evidence and information which may
be used in determining the kind and extent of the punishment
to be imposed, and evidence may be presented as to any mat-
ter that the court deems relevant to the sentence. 11 Although
§ 29-2521(2) dictates that the Nebraska Rules of Evidence
 9
     See State v. Sandoval, 280 Neb. 309, 788 N.W.2d 172 (2010). See, also,
     State v. Molina, 271 Neb. 488, 713 N.W.2d 412 (2006).
10
     See Jenkins, supra note 2.
11
     Id.
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                              STATE v. SCHROEDER
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apply when determining the aggravating circumstances alleged
by the information, it contains no such requirement for con-
sideration of mitigating circumstances. Because a sentencing
panel is required to consider and weigh any mitigating cir-
cumstances in imposing a sentence of death, the introduction
of evidence of the existence or nonexistence of these potential
mitigators has probative value to the sentence. Thus, the panel
could permit the State to present evidence to contradict poten-
tial mitigators even though Schroder failed to present affirma-
tive evidence.
   Schroeder argues the State’s evidence purported to rebut
the statutory mitigating circumstances was actually offered
to support uncharged aggravating circumstances. Specifically,
Schroeder alleges the State’s evidence was offered to show the
nonstatutory aggravating circumstance of future dangerous-
ness and “both prongs” 12 of § 29-2523(1)(d), which provides
a statutory aggravator when a murder was especially heinous,
atrocious, or cruel or manifested exceptional depravity by ordi-
nary standards of morality and intelligence.
   During the portion of the hearing devoted to mitigating
circumstances, the State’s evidence related to Berry’s murder.
Lundgren testified about her interview with Schroeder where
he described how and why he killed Berry. This same interview
was also described in the presentence investigation report. The
doctor who performed the autopsy on Berry explained that
Berry was killed by strangulation. Wilder explained the events
surrounding his discovery of Berry’s murder and Schroeder’s
reaction. Eppens explained that Schroeder told him he had pre-
viously informed correctional staff he did not want a cellmate
and joked, while Eppens was moving him following the dis-
covery of Berry’s unconscious body, “[T]his is what happens
when we watch UFC.” Additionally, through the testimony of
a TSCI employee, the State introduced a notarized writing in
which Schroeder confessed, explained his reasons for killing
Berry, and stated he would kill again if given another life term.
12
     Brief for appellant at 28.
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                         STATE v. SCHROEDER
                           Cite as 305 Neb. 527

   This evidence surrounding Berry’s murder was relevant
to the statutory mitigating circumstances the panel was
required to consider. The mitigating circumstances listed under
§ 29-2523(2) involve, in part, circumstances surrounding the
underlying crime. These circumstances include pressure or
influences which may have weighed on the defendant, poten-
tial influence on the defendant of extreme mental or emotional
disturbance at the time of the offense, potential victim partici-
pation or consent to the act, the defendant’s capacity to appre-
ciate the wrongfulness of the act at the time of the offense,
and any mental illness, defect, or intoxication which may have
contributed to the offense. 13 The State’s evidence informed
the panel’s analysis and was relevant to consideration of these
mitigators; and, as explained above, the panel had discretion to
hear this evidence.
   Schroeder fails to allege that the introduction of this evi-
dence influenced the panel’s finding of the existence of the
charged aggravator—namely that Schroeder had been convicted
of another murder, been convicted of a crime involving the use
or threat of violence to the person, or had a substantial prior
history of serious assaultive or terrorizing criminal activity. 14 It
is undisputed that Schroeder had previously been convicted of
the murder of Albers and was incarcerated for that crime at the
time of Berry’s killing. Schroeder does not challenge the pre-
sentation of evidence related to this aggravating circumstance
for failing to comply with the Nebraska Evidence Rules. 15
   The panel had discretion to hear any evidence relevant to
sentencing, the panel was required to consider mitigating cir-
cumstances even though Schroeder failed to allege or present
evidence in support of them, and the evidence presented by the
State was relevant to the panel’s review of these mitigators.
As such, the panel did not err in allowing the State to present
evidence on the existence of mitigating circumstances.
13
     § 29-2523(2).
14
     § 29-2523(1)(a).
15
     See § 29-2521(2).
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                            STATE v. SCHROEDER
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                    Weighing of Mitigating
                         Circumstances
   Schroeder next assigns the panel failed to properly con-
sider mitigating information contained within the presentence
investigation report and available from the State’s evidence.
Schroeder claims proper consideration of this evidence would
have led the panel to find additional statutory and nonstatutory
mitigating circumstances.
   [12] As explained, § 29-2521 requires a sentencing panel to
consider mitigating circumstances. Neb. Rev. Stat. § 29-2522
(Cum. Supp. 2018) describes the weighing of the aggravat-
ing and mitigating circumstances in imposing a sentence of
death and requires that the determination be in writing and
refer to the aggravating and mitigating circumstances weighed.
Accordingly, the sentencing order must specify the factors it
relied upon in reaching its decision and focus on the individual
circumstances of each homicide and each defendant. 16
   We first address Schroeder’s claims that the panel should
have applied additional nonstatutory mitigating evidence,
including (1) that the State had ulterior motives for pursu-
ing the death penalty to avoid and detract from potential civil
liability for failing to protect Berry, (2) that Schroeder was
institutionalized from consistent incarceration, and (3) that
Schroeder had used money elicited from his murder of Albers
to provide clothes and food for his family.
   [13,14] The U.S. Constitution does not require the sen-
tencing judge or judges to make specific written findings
with regard to nonstatutory mitigating factors. 17 In State v.
Jenkins, 18 we addressed an assignment of a sentencing panel
failing to address nonstatutory mitigators and explained that
16
     State v. Dunster, 262 Neb. 329, 631 N.W.2d 879 (2001).
17
     State v. Bjorklund, 258 Neb. 432, 604 N.W.2d 169 (2000), abrogated
     on other grounds, State v. Mata, 275 Neb. 1, 745 N.W.2d 229 (2008).
     Accord State v. Reeves, 234 Neb. 711, 453 N.W.2d 359, cert. granted and
     judgment vacated 498 U.S. 964, 111 S. Ct. 425, 112 L. Ed. 2d 409 (1990).
18
     Jenkins, supra note 2.
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we will not fault the panel for failing to discuss a nonstatu-
tory mitigating circumstance that it was not specifically asked
to consider.
   Additionally, the underlying facts Schroeder uses as sup-
port for these nonstatutory mitigators are included in the
presentence investigation report which the panel explained it
considered in determining his sentence. The panel also specifi-
cally acknowledged many of these facts in its sentencing order.
On the allegation that the State had ulterior motives due to
potential liability, the panel explained the cell Schroeder and
Berry shared was intended for a single inmate, Berry was set
for release 2 weeks after moving in with Schroeder, Schroeder
was serving a life sentence for Albers’ murder, and Schroeder
warned that issues might arise if he were incompatible with
whoever was assigned as his roommate. As to institutional-
ization, the panel described Schroeder’s current incarceration
for Albers’ murder and noted his dysfunctional childhood and
that “[h]e was involved in the juvenile court at a young age.”
Finally, on the use of money he attained from Albers’ murder,
the panel described that he took several thousand dollars from
Albers after leaving him for dead and “drove around the area,
paying off bills and making purchases.” It is clear the panel
considered and weighed these facts even though it did not state
a finding that they led to the specific nonstatutory mitigating
circumstances Schroeder presently claims.
   Because the panel was not required to make specific writ-
ten findings on the application of nonstatutory mitigating fac-
tors, and taking into account the panel’s consideration of
the facts Schroeder alleges support these factors, Schroeder’s
claims involving the nonstatutory mitigators do not demon-
strate reversible error.
   We next turn to Schroeder’s claim that the panel failed
in its analysis of statutory mitigating circumstances. Of the
statutory mitigating factors, Schroeder claims the panel should
have determined the following applied: Schroeder acted under
unusual pressures or influences or under the domination
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                            STATE v. SCHROEDER
                              Cite as 305 Neb. 527

of another person, 19 Berry’s murder was committed while
Schroeder was under the influence of extreme mental or emo-
tional disturbance, 20 and Berry was a participant in Schroeder’s
conduct or consented to the act. 21
   For Schroeder’s claims that he was under unusual pressures
or influences and extreme mental or emotional disturbance,
he first alleges the panel failed to acknowledge his efforts to
get Berry removed as a cellmate and his incompatibility with
Berry. He supports this allegation by referencing the panel’s
determination that Schroeder had calculated Berry’s murder for
several days and chose no method of obviating his annoyance.
Schroeder further quoted the panel’s explanation that finding
the kite in the trash “suggests a premeditative and depraved
mentality” in that Schroeder “did not ask that [Berry] be
moved” and in that Schroeder “did not tell the guards that . . .
Berry was in mortal danger if he were not moved.”
   Schroeder contends this determination and the findings
supporting it are contradicted by the evidence. Specifically,
Schroeder points to the summaries of his interviews with
Lundgren, included in the presentence investigation report,
wherein he told Lundgren that he had “‘told all of the staff’”
that he did not want Berry as a cellmate, that he told staff
members he was not compatible with Berry when they assigned
him to Schroeder’s cell, that a TSCI caseworker had tried to
get the assignment switched prior to Berry’s moving in, and
that corrections officers would laugh at the arrangement and
joke they were surprised Schroeder had not killed Berry yet.
Schroeder also points to Lundgren’s case synopsis noting that
the TSCI caseworker Schroeder described in his interview
explained that she did have concerns prior to Berry’s moving
into the cell based on a “‘gut feeling’” that the arrangement
would be “‘a bad idea’” but that she was unsuccessful in get-
ting it switched.
19
     See § 29-2523(2)(b).
20
     See § 29-2523(2)(c).
21
     See § 29-2523(2)(f).
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                      STATE v. SCHROEDER
                        Cite as 305 Neb. 527

   However, the panel’s statements that Schroeder did not ask
for Berry to be moved and did not warn that Berry was in
mortal danger are not contradicted by Lundgren’s summaries.
Lundgren’s summary of Schroeder’s interview only described
Schroeder’s assertions that he told staff prior to Berry’s mov-
ing in that he did not want Berry as a cellmate and was
incompatible with him. Lundgren’s summary did not describe
that Schroeder asserted he continued these complaints after
the move was made and did not allege he made any actual
requests for Berry to be moved. Moreover, there is nothing in
Schroeder’s description of his interactions with TSCI officials
where he indicated Berry was in mortal danger if they con-
tinued to share the cell. While Schroeder alleged corrections
officers would joke they were surprised he had not killed Berry
yet, such statements do not imply that Schroeder requested that
Berry be moved or that they believed or had reason to believe
that Berry was actually in mortal danger. Similarly, while
the TSCI caseworker attempted to get Berry’s assignment to
Schroeder’s cell switched prior to his move, there is nothing
indicating that she was doing so at Schroeder’s request or that
her “‘gut feeling’” was based upon a belief such an arrange-
ment might lead to Berry’s death.
   The panel reviewed the presentence investigation report and
Lundgren’s summaries prior to determining whether there were
mitigating circumstances. The panel’s findings that Schroeder
did not request Berry’s removal from his cell and did not warn
officials of potential danger to Berry is uncontradicted by the
report. Instead, the report shows that Schroeder acted with
premeditation and depravity in that Schroeder explained he had
made up his mind to kill Berry days before he did so and in
that he made no real attempts to avoid this result, even having
made the decision to discard the kite which could have helped
avoid the killing.
   Schroeder’s explanations in his interview that he killed
Berry because he was unclean and annoying do not rise to the
level of accounts of unusual pressure or influence or extreme
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                            STATE v. SCHROEDER
                              Cite as 305 Neb. 527

mental or emotional disturbance. Nothing in the record indi-
cates that Schroeder continually sought Berry’s removal
from the cell or that any such requests were unheeded by
TSCI staff.
   Schroeder references the effect incarceration can have on
inmates in support of his unusual pressures or influences and
extreme mental or emotional disturbance claims. Schroeder
cites to several articles, while acknowledging he did not pro-
vide them to the court because he did not present any evidence,
which discuss the effects of institutionalization and incarcera-
tion in solitary confinement on an inmate’s mental health as
well as articles and reports of security and staffing issues at
TSCI and DCS.
   [15] We have previously addressed the effect incarceration
and, specifically, isolated confinement can have on individu-
als. In Jenkins, we analyzed the application of a nonstatutory
mitigating factor of solitary confinement and quoted the under-
standing that “‘[y]ears on end of near-total isolation exact a
terrible price.’” 22 However, we also noted that prison officials
must have discretion to decide that in some instances, tem-
porary solitary confinement is a useful or necessary means to
impose discipline and to protect prison employees and other
inmates. 23 Because of the defendant’s own extensive and vio-
lent actions in that case, the prison officials needed to have
some recourse to deal with such an inmate, and we found that
it was reasonable in not rewarding such behavior by consider-
ing the resulting confinement as a mitigating factor. 24 For the
same reasons, the mere identification of a history of incar-
ceration, without more, is insufficient to allege unusual pres-
sures or influences or establish extreme mental or emotional
22
     Jenkins, supra note 2, 303 Neb. at 727, 931 N.W.2d at 888, quoting
     Davis v. Ayala, 576 U.S. 257, 135 S. Ct. 2187, 192 L. Ed. 2d 323 (2015)
     (Kennedy, J., concurring).
23
     Jenkins, supra note 2.
24
     Id.
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                              STATE v. SCHROEDER
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disturb­ance. Schroeder’s incarceration was due to his own
actions, including, most recently, his murder of Albers.
   Contrary to Schroeder’s assertions and as discussed in our
analysis of Schroeder’s claims of the nonstatutory mitigat-
ing factors of institutionalization and the State’s alleged ulte-
rior motive to avoid possible litigation, the underlying facts
of Schroeder’s claims were acknowledged and weighed by
the court. In its order, the panel acknowledged that the cell
Schroeder and Berry shared was intended for a single inmate,
Berry was set for release 2 weeks after moving in with
Schroeder, Schroeder was serving a life sentence for Albers’
murder, and Schroeder had a history of incarceration includ-
ing his history within the juvenile court system and his current
sentence for Albers’ murder. The panel reasonably found that
on their own, these facts and the reality of the effect incarcera-
tion can have on individuals were insufficient to establish that
Schroeder acted under unusual pressures or influences or was
under extreme mental or emotional disturbance. Under our de
novo review, we reach the same conclusion.
   Schroeder’s remaining claim, that the panel erred in fail-
ing to find Berry was a participant in Schroeder’s conduct
or consented to the act, is without merit. Schroeder supports
this proposition by noting, “Berry complied with Schroeder’s
request that he turn the chair around and face away from
Schroeder after Schroeder expressed extreme annoyance with
his behavior.” 25 However, Berry’s facing away from Schroeder
does not indicate participation or consent to his murder.
Schroeder expressed frustration and requested Berry to turn
away from him. How Berry would have understood this as
Schroeder’s asking for aid in his strangulation and not as a
method to avoid conflict is unclear. Schroeder offers no further
argument to support this mitigating circumstance, and we agree
with the panel’s finding that there was no evidence establishing
this mitigating factor.
25
     Brief for appellant at 40.
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                            STATE v. SCHROEDER
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              Duty to Request DCS Chapter 83
                       Custody Reports
   Schroeder claims the panel had a duty to request additional
records of Schroeder’s incarceration from DCS. These records
are required to be kept by DCS under Neb. Rev. Stat. § 83-178
(Reissue 2014) and include records concerning Schroeder’s
background, conduct, associations, and family relationships;
records regarding Schroeder’s “Central Monitoring,” 26 which
may be relevant to the propriety of his placement with Berry;
and any medical or mental health records.
   [16-18] When an offender has been convicted of first degree
murder and waives the right to a jury determination of an
alleged aggravating circumstance, the court must order a pre-
sentence investigation of the offender and the panel must
consider a written report of such investigation in its sentenc-
ing determination. 27 The presentence investigation and report
shall include, when available, any submitted victim statements
and an analysis of the circumstances attending the commis-
sion of the crime and the offender’s history of delinquency or
criminality, physical and mental condition, family situation and
background, economic status, education, occupation, and per-
sonal habits. 28 The investigation and report may also include
any other matters the probation officer deems relevant or the
court directs to be included. 29
   In this case, the court ordered a presentence investigation
and report, a report was prepared, and the panel considered it
during its sentence determination. Schroeder does not allege
this report failed to analyze and present any of the areas
required by § 29-2261(3). Instead, Schroeder claims the court
had a duty to request the presentence investigation report to
include specific incarceration records. Schroeder relies on State
26
     Id. at 42.
27
     § 29-2521(2) and Neb. Rev. Stat. § 29-2261(1) (Reissue 2016).
28
     § 29-2261(3).
29
     Id.
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v. Dunster 30 for this claim that the panel should have requested
additional documents.
   In that case, the defendant was sentenced to death after
pleading guilty to first degree murder. 31 Prior to sentencing,
the district court instructed the probation officer conducting
the presentence investigation to include information in the
possession of DCS as part of the report. 32 The court explained
that access to this information was restricted by law and that it
would not be released to the public except upon written order. 33
On appeal, the defendant assigned the district court’s consider-
ation of this information, which included confidential mental
health information provided by DCS, as reversible error. 34
However, we found the district court had given adequate notice
to the defendant of its intent to consider such evidence to sat-
isfy his due process rights. 35
   Additionally, when the bill of exceptions was completed in
that case, the DCS records were not included. As a result, we
determined that in our de novo review, we could request and
consider the additional documents just as the district court had
requested and considered them. 36 In reaching this determina-
tion, we noted that our request of these documents did not
indicate in advance how we would rule on appeal but merely
followed our statutory requirements for review and honored the
intent of the Legislature to provide “‘the most scrupulous stan-
dards of fairness and uniformity’” in reviewing the imposition
of a sentence of death. 37
30
     Dunster, supra note 16.
31
     Id.
32
     Id.
33
     Id.
34
     Id.
35
     Id.
36
     Id.
37
     Id. at 372, 631 N.W.2d at 913.
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                             STATE v. SCHROEDER
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   Dunster neither explicitly nor implicitly required a lower
court to receive and review documents of a defendant’s prior
incarceration. Instead, it only evaluated the process of a district
court seeking to consider specific documents during a sentenc-
ing proceeding and our ability to review the same information
upon which the lower court relied. 38 Accordingly, Dunster did
not add further requirements for the preparation of a presen-
tence investigation report under § 29-2261(3).
   Because the district court complied with its duties under
§ 29-2261(1) in requesting the presentence investigation and
report, because the presentence report included the requisite
analysis of the § 29-2261(3) elements, and because there is no
requirement that a sentencing court must request access to spe-
cific § 83-178 DCS records, the district court did not err by not
requesting that the DCS records be included in the presentence
investigation report.
                Sufficiency of Safeguards to
                 Prevent Arbitrary Results
   Schroeder claims Nebraska’s death penalty is unconstitu-
tional as applied to him under the 8th and 14th Amendments
to the U.S. Constitution and article I, §§ 3, 9, and 15, of
the Nebraska Constitution. Schroeder argues that insufficient
safeguards exist to prevent arbitrary results when, as here, a
defendant waives his right to counsel and refuses to introduce
mitigating or proportionality evidence or argument.
   [19,20] An accused has a state and federal constitutional
right to be represented by an attorney in all critical stages of a
criminal prosecution which can lead to a sentence of confine-
ment. 39 However, a defendant may waive this right to counsel
38
     Dunster, supra note 16.
39
     See, U.S. Const. amends. VI and XIV; Neb. Const. art. I, § 11; Scott v.
     Illinois, 440 U.S. 367, 99 S. Ct. 1158, 59 L. Ed. 2d 383 (1979); Argersinger
     v. Hamlin, 407 U.S. 25, 92 S. Ct. 2006, 32 L. Ed. 2d 530 (1972); Jenkins,
     supra note 2; State v. Wilson, 252 Neb. 637, 564 N.W.2d 241 (1997);
     State v. Dean, 246 Neb. 869, 523 N.W.2d 681 (1994), overruled on other
     grounds, State v. Burlison, 255 Neb. 190, 583 N.W.2d 31 (1998).
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                             STATE v. SCHROEDER
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so long as the waiver is made knowingly, voluntarily, and
intelligently. 40
   [21-23] The same constitutional provisions that provide
a defendant the right to counsel also guarantee the right of
the accused to represent himself or herself. 41 This right to
self-representation plainly encompasses certain specific rights
of the defendant to have his voice heard, including that the
pro se defendant must be allowed to control the organiza-
tion and content of his own defense. 42 We have previously
explained that such control may include a waiver of the right
to present mitigating evidence during sentencing in a death
penalty case. 43
   Schroeder does not challenge the validity of his waiver of
counsel for the penalty phase or his election not to present miti-
gating evidence or proportionality argument. Instead, Schroeder
argues that the exercise of the right to self-­representation
and, derived therefrom, the right to waive the presentation
of evidence and argument conflicted with the constitutional
restrictions against cruel and unusual punishment. Specifically,
Schroeder addresses the effect such waivers have on the pro-
portionality review by the sentencing panel. To establish the
cruelty and unusualness of such punishment, Schroeder notes
first that the proportionality requirement under Neb. Rev.
Stat. §§ 29-2521.01 to 29-2521.04 (Cum. Supp. 2018) only
requires the sentencing panel to review those cases in which
the death penalty was imposed. Schroeder also asserts propor-
tionality review is further limited depending on whether jury
determinations in the reviewed cases were waived because,
40
     Jenkins, supra note 2; State v. Hessler, 274 Neb. 478, 741 N.W.2d       406
     (2007).
41
     Faretta v. California, 422 U.S. 806, 95 S. Ct. 2525, 45 L. Ed. 2d       562
     (1975); Jenkins, supra note 2; Wilson, supra note 39; State v. Green,   238
     Neb. 328, 470 N.W.2d 736 (1991).
42
     McKaskle v. Wiggins, 465 U.S. 168, 104 S. Ct. 944, 79 L. Ed. 2d         122
     (1984); Dunster, supra note 16; Wilson, supra note 39.
43
     Dunster, supra note 16.
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                           STATE v. SCHROEDER
                             Cite as 305 Neb. 527

when they are waived, a sentencing panel is required to issue
written findings of fact as to any proven aggravating circum-
stances, but when there is no waiver, the jury does not issue
such analysis. Schroeer argues that when a defendant waives
counsel and refuses to meaningfully participate, the record on
which the panel makes its proportionality determination is lim-
ited to what it requests and the State presents, which has the
potential to be limited and biased in favor of the imposition of
a death sentence.
   [24,25] Because a death sentence is different from any
other criminal penalty 44 and no system based on human judg-
ment is infallible, we have taken, and should continue to
take, the extra step to ensure fairness and accuracy with the
imposition of the death penalty. 45 Taking this into account,
the Legislature has enacted a statutory scheme to provide
additional safeguards, 46 and in interpreting these statutes, we
have followed the fundamental principle of statutory construc-
tion that penal statutes are to be strictly construed in favor of
the defendant. 47
   [26] Part of this statutory scheme, as explained, requires a
court to order a presentence investigation report. 48 The sentenc-
ing panel must consider this report in reaching its sentence.
Thus, contrary to Schroeder’s argument, even if the State pre­
sents evidence in favor of a specific sentence and the defendant
declines to present contrary evidence, the court receives and
must consider independent information from the report.
   [27,28] In a death penalty case, the sentencing panel is
required to review this report and determine whether it contra-
dicts the State’s evidence of aggravating factors and whether
any mitigating circumstances exist, including specifically
44
     State v. Hochstein and Anderson, 262 Neb. 311, 632 N.W.2d 273 (2001).
45
     Id.
46
     Neb. Rev. Stat. §§ 29-2519 to 29-2546 (Cum. Supp. 2018).
47
     Hochstein and Anderson, supra note 44.
48
     §§ 29-2261(1) and 29-2521(2).
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                            STATE v. SCHROEDER
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delineated statutory mitigators. 49 While the State must prove the
aggravating circumstances beyond a reasonable doubt, 50 there
is no burden of proof with regard to mitigating circumstances. 51
Accordingly, the panel’s evaluation of the independently com-
piled presentence investigation report and any evidence the
defendant chooses to introduce is under the less restrictive
mitigation standard and provides another safeguard to ensure
fairness and accuracy in a death penalty determination.
   [29-32] Once the panel makes its determinations about the
existence of aggravating and mitigating circumstances, the
panel is then required to undertake a proportionality review.
This review looks at whether the sentence of death is excessive
or disproportionate to the penalty imposed in similar cases,
considering both the crime and the defendant. 52 Proportionality
review is not constitutionally mandated. 53 It exists in Nebraska
by virtue of §§ 29-2521.01 to 29-2521.04, which direct this
court to conduct a proportionality review in each appeal in
which a death sentence is imposed. 54 A court’s proportionality
review spans all previous cases in which a sentence of death is
imposed and is not dependent on which cases are put forward
by the parties. 55
   Schroeder takes issue with proportionality review requiring
a panel to compare only those cases in which the death penalty
was imposed. 56 Instead, Schroeder argues the statutory scheme
explicitly requires review of all homicide cases regardless of
the resulting sentence.
49
     §§ 29-2521 to 29-2523.
50
     Torres, supra note 3.
51
     State v. Vela, 279 Neb. 94, 777 N.W.2d 266 (2010); State v. Victor, 235
     Neb. 770, 457 N.W.2d 431 (1990).
52
     § 29-2522(3).
53
     State v. Gales, 269 Neb. 443, 694 N.W.2d 124 (2005).
54
     Id.
55
     See id.
56
     See State v. Palmer, 224 Neb. 282, 399 N.W.2d 706 (1986), overruled on
     other grounds, State v. Chambers, 233 Neb. 235, 444 N.W.2d 667 (1989).
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                              STATE v. SCHROEDER
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   It is unclear how Schroeder is arguing this fits under his
assignment alleging unconstitutionality in the interplay of
his waiver of counsel and election not to present evidence
or argument with Nebraska’s capital sentencing scheme. The
introduction of further evidence or whether or not Schroeder
was represented by counsel does not affect what previous
cases the panel was required to consider. In any case, we
decline Schroeder’s invitation to overrule our decision in State
v. Palmer 57 which interpreted §§ 29-2521.01 to 29-2521.04 to
only require review of previous cases in which the death pen-
alty was imposed.
   Additionally, we are unconvinced by Schroeder’s claim that
the proportionality review is unconstitutionally flawed due
to having less analysis of the reviewed cases in which a jury
determines the existence of the aggravating circumstance than
of the reviewed cases in which a sentencing panel makes the
determination. Again, it is unclear how Schroeder relates this
alleged flaw to this assignment. If Schroeder is claiming that
waiver of counsel and lack of argument would prohibit the
panel from taking into account that previous aggravation deter-
minations were decided by juries, this information would be
apparent from the previous opinions and would be able to be
considered by the panel independently of whether the defend­
ant or an advocate explained such difference to the panel.
   [33,34] Moreover, even when a jury determines the exis-
tence of an aggravating circumstance, a sentencing panel is
required to put in writing its consideration of (1) whether the
determined aggravating circumstance justifies the imposition
of a sentence of death, (2) whether mitigating circumstances
exist, and (3) whether a sentence of death would be excessive
or disproportionate to penalties imposed in similar cases. 58 This
writing must specifically refer to the aggravating and mitigat-
ing circumstances weighed in the determination of the panel. 59
57
     Id. See, also, State v. Gales, supra note 53.
58
     § 29-2522.
59
     Id.
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                           STATE v. SCHROEDER
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As such, the basis of Schroeder’s argument that cases where
a jury determines the existence of aggravating circumstances
provide insufficient information for comparison in a propor-
tionality review is without merit.
   [35-38] Considering all of the above, Nebraska’s capital
sentencing scheme provides additional statutory steps and con-
siderations to ensure fairness and accuracy, and these safe-
guards exist regardless of a defendant’s strategy at the pen-
alty phase. Due to this statutory scheme, a defendant cannot
“choose” the death penalty. The sentencing decision rests
with the court alone. 60 In order to exercise this authority, the
statutory scheme requires that a sentencing panel consider not
only evidence and argument presented by the parties but also
an independently compiled presentence investigation report to
determine whether the alleged aggravating circumstance exists,
determine whether any mitigating factors are present which
would weigh against the imposition of the death penalty, and
conduct a proportionality review weighing the aggravating and
mitigating factors and comparing the facts to previous cases
where the death penalty was imposed. 61 These considerations
exist and are weighed regardless of the evidence presented by
the parties or their arguments.
   [39,40] A defendant is entitled to present a defense and is
guaranteed the right to choose the objectives for that defense. 62
As previously stated, the self-represented defendant must be
allowed to control the organization and content of his own
defense. 63 However, Schroeder suggests that in a death pen-
alty case, the substantial nature of the proceedings requires
an advocate in opposition to a sentence of death irrespective
of the defendant’s chosen objective. To this end, he suggests
§§ 29-2519 to 29-2546 implicitly require the appointment of a
60
     Dunster, supra note 16.
61
     See Torres, supra note 3.
62
     McCoy v. Louisiana, ___ U.S. ___, 138 S. Ct. 1500, 200 L. Ed. 2d 821
     (2018); Jenkins, supra note 2.
63
     Dunster, supra note 16.
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                            STATE v. SCHROEDER
                              Cite as 305 Neb. 527

guardian ad litem to present evidence and argument as to why
the death penalty should not be imposed.
   [41] This suggestion is similar to that addressed in Dunster. 64
The defendant therein had waived trial counsel for the penalty
stage and chose not to present any mitigating evidence. On
appeal, he claimed the court should have appointed “amicus
counsel” to advocate against the imposition of the death pen-
alty by presenting evidence and “‘argu[ing] for life,’” which is
identical to the role Schroeder now envisions for an appointed
guardian ad litem. 65 As noted in Dunster, when a defendant
waives counsel and the presentation of mitigating evidence,
the appointment of an advocate to present evidence and argue
against the imposition of a sentence overrides that defendant’s
constitutional right to control the organization and content of
his or her own defense during sentencing.
   [42,43] A criminal defendant has the right to waive counsel
and present his or her own defense. 66 In a death penalty case,
this includes the right of the defendant to elect not to present
additional evidence or argument during the penalty proceed-
ings. Even if a defendant makes such waiver and election, the
Legislature has enacted safeguards to ensure fairness and accu-
racy in the resulting sentence. As explained above, these safe-
guards apply regardless of the defense strategy an individual
defendant implements. Therefore, Schroeder’s assignment that
Nebraska’s capital sentencing scheme is unconstitutional due
to insufficient safeguards to prevent arbitrary results when a
defendant waives counsel and elects not to present evidence or
argument fails.
                   Excessiveness and
                Proportionality Review
  [44,45] In reviewing a sentence of death, we conduct
a de novo review of the record to determine whether the
64
     Id.
65
     Id. at 361, 631 N.W.2d at 906.
66
     See Dunster, supra note 16.
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                             STATE v. SCHROEDER
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aggravating and mitigating circumstances support the imposi-
tion of the death penalty. 67 In so doing, we consider whether
the aggravating circumstances justify imposition of a sentence
of death and whether any mitigating circumstances found to
exist approach or exceed the weight given to the aggravat-
ing circumstances. 68
   We first note Schroeder does not contest the factual basis
for the § 29-2523(1)(a) aggravation allegation that Schroeder
was convicted of Albers’ murder. It is undisputed that in 2006,
Schroeder murdered Albers, who was at the time Schroeder’s
75-year-old previous employer. It is also undisputed that
Albers was robbed and that Schroeder had made the decision
to kill Albers days before the robbery. Schroeder threatened
and beat Albers, tied him up, threw him in the back of a
pickup, and dumped him in an abandoned well, leaving him
for dead. Based upon our de novo review, we determine this
murder conviction, which was proved beyond a reasonable
doubt at the sentencing hearing, is sufficient as an aggravating
circumstance under § 29-2523(1)(a) to justify the imposition
of the death penalty. In coordination with our analysis con-
cerning the panel’s mitigating circumstance findings, we also
agree with the panel’s determination that the applicable statu-
tory and nonstatutory circumstances apparent from the record
do not approach or exceed the aggravating circumstance in
this case.
   [46-48] In addition, we are required, upon appeal, to deter-
mine the propriety of a death sentence by conducting a propor-
tionality review, comparing the aggravating and mitigating cir-
cumstances with those present in other cases in which a court
imposed the death penalty. 69 The purpose of this review is to
ensure that the sentences imposed in this case are no greater
than those imposed in other cases with the same or similar
67
     Torres, supra note 3.
68
     Id.
69
     Id.
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                             STATE v. SCHROEDER
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circumstances. 70 Our proportionality review looks only to other
cases in which the death penalty has been imposed and requires
us to compare the aggravating and mitigating circumstances of
the case on appeal with those present in those other cases. 71
   In this case, we have reviewed our relevant decisions on
direct appeal from other cases in which the death penalty was
imposed. 72
   Like the sentencing panel, we find Dunster particularly
pertinent to our review. 73 The defendant therein was convicted
of murdering his cellmate by strangling him with an electrical
cord. 74 The defendant had previously been convicted of the
earlier murder of a woman while attempting to collect a debt
from her husband, and he had confessed to a different murder
of another inmate while incarcerated for the first murder. 75
At the penalty phase, the State alleged a single aggravating
circumstance of § 29-2523(1)(a) and presented evidence of
the two previous killings. 76 After the trial court sentenced the
defendant to death, we affirmed. 77 Such factual basis is similar
to that in the instant case. As did the defendant in Dunster,
Schroeder murdered his cellmate by strangulation. Schroeder’s
previous murder of Albers was also pursuant to a plan to take
money from his victim.
70
     See id.
71
     Id.
72
     See, e.g., Jenkins, supra note 2; Torres, supra note 3; State v. Ellis, 281
     Neb. 571, 799 N.W.2d 267 (2011); Hessler, supra note 40; Dunster, supra
     note 16; State v. Lotter, 255 Neb. 456, 586 N.W.2d 591 (1998), modified
     on denial of rehearing 255 Neb. 889, 587 N.W.2d 673 (1999); State v.
     Williams, 253 Neb. 111, 568 N.W.2d 246 (1997); State v. Ryan, 233 Neb.
     74, 444 N.W.2d 610 (1989); State v. Joubert, 224 Neb. 411, 399 N.W.2d
     237 (1986); State v. Otey, 205 Neb. 90, 287 N.W.2d 36 (1979).
73
     Dunster, supra note 16.
74
     Id.
75
     Id.
76
     Id.
77
     Id.
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                               STATE v. SCHROEDER
                                 Cite as 305 Neb. 527

   Schroeder attempts to differentiate his case from Dunster
by emphasizing that while only one aggravating circumstance
was alleged in Dunster, the allegation therein concerned
two previous murders. Additionally, Schroeder argues those
underlying murders were committed with more serious facts,
including that there was suspected sexual assault of one of
the victims.
   First, it is not evident that the underlying murders in Dunster
included any more or less serious facts surrounding their
execution. Schroeder threatened, beat, and robbed Albers and
threw him bound and alive into a well to die. The murders the
defendant in Dunster committed involved binding, beating,
killing, and possible sexual assault. In both cases, the defend­
ants acted with violence toward the persons.
   [49,50] Additionally, while there were two underlying mur-
ders in Dunster, this does not mean Dunster cannot be used
in a proportionality review. A proportionality review does not
require that a court “color match” cases precisely. 78 It would
be virtually impossible to find two murder cases which are the
same in all respects. 79 Instead, the question is simply whether
the cases being compared are sufficiently similar, considering
both the crime and the defendant, to provide the court with a
useful frame of reference for evaluating the sentence in this
case. 80 As the factual connections show, Dunster is sufficiently
similar for purposes of evaluating proportionality.
   [51-53] Along the same lines, Schroeder attempts to distin-
guish his case from others cited by the sentencing panel and
reviewed on appeal by noting that the majority of those cases
had multiple aggravating factors. However, we have established
that one aggravating circumstance may be sufficient under our
statutory system for the imposition of the death penalty. 81 In
78
     Ellis, supra note 72.
79
     Id.
80
     Id.
81
     Dunster, supra note 16.
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                             STATE v. SCHROEDER
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our proportionality review, the evaluation of whether the death
penalty should be imposed in a specific case is not a mere
counting process of “X” number of aggravating circumstances
and “Y” number of mitigating circumstances and, instead, asks
whether the reviewed cases are sufficiently similar to provide
a useful reference for that evaluation. 82 Thus, even though
other cases may involve additional or different aggravating
circumstances, they may still be sufficiently similar to provide
such reference.
   Having reviewed our previous cases which have affirmed
the imposition of a death penalty and compared the aggra-
vating and mitigating circumstances present in those cases,
we are persuaded that the sentence imposed in this case is
not greater than those imposed in other cases with the same
or similar circumstances. Accordingly, we affirm Schroeder’s
death sentence.
                        CONCLUSION
  In consideration of all of the above, Schroeder’s conviction
and sentence for first degree murder are affirmed.
                                                   Affirmed.
  Freudenberg, J., not participating.
82
     See, Ellis, supra note 72; Dunster, supra note 16.
