                                 IN THE

    SUPREME COURT OF THE STATE OF ARIZONA
                           STATE OF ARIZONA,
                               Appellee,

                                    v.

                         JOSEPH JAVIER ROMERO,
                                Appellant.

                           No. CR-15-0039-PR
                          Filed January 20, 2016

            Appeal from the Superior Court in Pima County
               The Honorable Deborah Bernini, Judge
                        No. CR20103531-001

             Opinion of the Court of Appeals, Division Two
                236 Ariz. 451, 341 P.3d 493 (App. 2014)
              VACATED IN PART AND REMANDED

COUNSEL:

Mark Brnovich, Arizona Attorney General, John R. Lopez IV, Solicitor
General, Joseph T. Maziarz, Chief Counsel, Criminal Appeals Section, Tanja
K. Kelly (argued), Assistant Attorney General, Tucson, Attorneys for State
of Arizona

Steven R. Sonenberg, Pima County Public Defender, Abigail Jensen
(argued), Assistant Public Defender, Tucson, Attorneys for Joseph Javier
Romero

Amy Kalman (argued) and Mikel Steinfeld, Maricopa County Public
Defender’s Office, Phoenix, and Kathleen Brody, Osborn Maledon, P.A.,
Phoenix, Attorneys for Amicus Curiae Arizona Attorneys for Criminal
Justice

CHIEF JUSTICE BALES authored the opinion of the Court, in which VICE
CHIEF JUSTICE PELANDER and JUSTICES BRUTINEL, TIMMER, and
BERCH (RETIRED) joined.
                           STATE V. ROMERO
                           Opinion of the Court

CHIEF JUSTICE BALES, opinion of the Court:

¶1            The State’s evidence supporting the conviction of Joseph
Javier Romero included testimony by a firearms examiner, based on a
toolmark comparison, that a certain pistol had fired six shell casings found
at the murder scene. We consider whether the trial court abused its
discretion by precluding Romero from offering expert testimony that
firearms examiners use subjective rather than scientifically rigorous
methods in drawing conclusions from indentations on shell casings.
Because Romero’s expert witness was qualified and his testimony would
have been helpful to the jury in understanding the evidence, the trial court
erred in excluding the testimony.

                                     I.

¶2             In June 2000, a man was killed by two gunshots. Although
witnesses did not see the shooting, they heard gunshots and saw two or
three men flee in a dark Ford Ranger or Mazda pickup truck. Police found
six spent .40-caliber shell casings and bullet fragments at the murder scene.
A cell phone was also found next to the victim’s body.

¶3           Nearly one month later, police officers stopped Romero for
reasons unrelated to the murder. He possessed the magazine for a .40-
caliber Glock pistol. The officers subsequently found a .40-caliber Glock
pistol without its magazine along the path Romero had traveled just before
encountering them. Police retained the pistol and the magazine.

¶4            Seven years later, a “cold case’” investigative unit inspected
the cell phone and traced it to Robert E. and, through him, to Romero.
Robert E. told police that, while a college student in 2000, he had known a
person named “Joe” who supplied him drugs and sometimes borrowed
Robert E.’s black Ford Ranger. Robert E. recalled that he had loaned his
pickup truck to Joe in the summer of 2000, possibly June, and Joe had kept
it longer than expected.

¶5             Frank Powell, a police firearms expert, examined the six .40-
caliber shell casings found at the murder scene and concluded that they
were all fired from the same gun. Later, Powell test-fired the Glock pistol
recovered when the police stopped Romero in July 2000. Comparing


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                            STATE V. ROMERO
                            Opinion of the Court

indentations on the shell casings, Powell concluded that this pistol had fired
the casings found at the murder scene.

¶6            Romero was indicted for first degree murder. The jury hung
on the charge, resulting in a mistrial. Before his retrial, Romero moved to
preclude Powell from testifying, arguing that the firearm examiner’s
conclusions lacked the reliability required by Arizona Rule of Evidence 702
and Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993). At a
hearing on this motion, the trial court reviewed a transcript of Powell’s
testimony at Romero’s first trial and also considered testimony by Dr. Ralph
Haber, a defense expert. Dr. Haber was not offered to testify whether
Powell had correctly analyzed the toolmarks on the shell casings. Instead,
Dr. Haber, based on his expertise in the broader field of experimental
design, criticized the scientific reliability of drawing conclusions by
comparing toolmarks.

¶7            The court denied Romero’s motion, finding that Powell was
qualified as an expert in the field of firearms examination and that his
opinions resulted from reliable principles and methods. It also granted the
State’s motion to preclude Dr. Haber from testifying as a defense expert at
the second trial, reasoning that Dr. Haber was not qualified as an expert in
firearms identification and, alternatively, that his testimony would
impermissibly invite the jury to revisit Daubert issues decided by the judge
with regard to Powell’s testimony.

¶8             At Romero’s second trial, Powell testified that the shell
casings from the murder scene “matche[d] very well” with the casings from
test-firing the Glock pistol. He therefore concluded that the casings from
the murder scene were fired from the Glock that the police found when they
stopped Romero in July 2000. The jury acquitted Romero of first degree
murder but convicted him of the lesser-included offense of second degree
murder. The trial court sentenced Romero to a presumptive term of sixteen
years’ imprisonment.

¶9             In affirming Romero’s conviction and sentence, a divided
panel of the court of appeals held that the trial court had not abused its
discretion in admitting Powell’s testimony or in precluding Dr. Haber from
testifying. State v. Romero, 236 Ariz. 451, 457–60 ¶¶ 18-32, 341 P.3d 493, 499–
502 (App. 2014). Specially concurring, one judge concluded that the trial


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                            STATE V. ROMERO
                            Opinion of the Court

court had erred by precluding Dr. Haber’s testimony, but that the error was
harmless. Id. at 469 ¶ 69, 341 P.3d at 511 (Eckerstrom, J., concurring).

¶10           We granted Romero’s petition for review solely with regard
to the preclusion of Dr. Haber’s testimony because Rule 702’s standard for
admitting expert testimony is a recurring issue of statewide importance.
We have jurisdiction pursuant to Article 6, Section 5(3) of the Arizona
Constitution and A.R.S. § 12-120.24.

                                      II.

¶11            We review a trial court’s exclusion of evidence for an abuse of
discretion, and we review de novo the interpretation of the Rules of
Evidence. A court abuses its discretion by committing an error of law. State
v. Bernstein, 237 Ariz. 226, 228 ¶ 9, 349 P.3d 200, 202 (2015). As the
proponent of Dr. Haber’s expert testimony, Romero bears the burden of
establishing its admissibility by a preponderance of the evidence. Id.

                                      A.

¶12             Arizona Rule of Evidence 702 allows an expert witness to
testify if, among other things, the witness is qualified and the expert’s
“scientific, technical, or other specialized knowledge will help the trier of
fact to understand the evidence . . . .” Trial courts serve as the “gatekeepers”
of admissibility for expert testimony, with the aim of ensuring such
testimony is reliable and helpful to the jury. Id. cmt. (2012).

¶13            The trial court here concluded that Dr. Haber was not
qualified to testify as an expert in firearms identification. In affirming, the
court of appeals noted that Dr. Haber, although having reviewed the
literature on firearms identification, had not previously been retained as an
expert on firearms identification, conducted a toolmark analysis, attempted
to identify different firearms, or conducted research on firearms
identification. 236 Ariz. at 458 ¶¶ 23-25, 341 P.3d at 500.

¶14            The issue, however, is not whether Dr. Haber was qualified
as an expert in firearms identification, but instead whether he was qualified
in the area of his proffered testimony — experimental design. Here, the
trial court determined that Powell was qualified to offer an expert opinion
that the shell casings were all fired from the same Glock. But Romero did

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                            STATE V. ROMERO
                            Opinion of the Court

not offer Dr. Haber as an expert in firearms identification to challenge
whether Powell had correctly performed his analysis or formed his
opinions. Instead, Dr. Haber’s testimony was proffered to help the jury
understand how the methods used by firearms examiners in performing
toolmark analysis differ from the scientific methods generally employed in
designing experiments.

¶15             Under Rule 702, when one party offers an expert in a
particular field (here, the State’s presentation of Powell as an expert in
firearms identification) the opposing party is not restricted to challenging
that expert by offering an expert from the same field or with the same
qualifications. The trial court should not assess whether the opposing
party’s expert is as qualified as — or more convincing than — the other
expert. Instead, the court should consider whether the proffered expert is
qualified and will offer reliable testimony that is helpful to the jury. Cf.
Bernstein, 237 Ariz. at 230 ¶ 18, 349 P.3d at 204 (noting that when the
reliability of an expert’s opinion is a close question, the court should allow
the jury to exercise its fact-finding function in assessing the weight and
credibility of the evidence).

¶16            The gist of Dr. Haber’s proffered testimony was that the
methods generally used in conventional toolmark analysis fall short of
scientific standards for experimental design. Dr. Haber’s testimony was
therefore directed at the scientific weight that should be placed on the
results of Powell’s tests. Such questions of weight are emphatically the
province of the jury to determine. E.g., State v. Lehr, 201 Ariz. 509, 517
¶¶ 24–29, 38 P.3d 1172, 1180 (2002). The trial court erred by focusing on
whether Dr. Haber was qualified as an expert in firearm identification
rather than considering the proper scope of his proffered testimony —
experimental design.

                                     B.

¶17           We turn to whether Dr. Haber was qualified to opine on the
experimental design of toolmark analysis generally, and how it contrasts
with other experimental designs rooted in the scientific method. Under
Rule 702, a witness may be qualified based on “knowledge, skill,
experience, training, or education.” For a witness to be qualified as an
expert, he or she need only possess “skill and knowledge superior to that
of [people] in general.” State v. Girdler, 138 Ariz. 482, 490, 675 P.2d 1301,

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                             STATE V. ROMERO
                             Opinion of the Court

1309 (1983) (quoting State v. Watson, 114 Ariz. 1, 12, 559 P.2d 121, 132 (1976)).
Careful study may suffice to qualify an expert if it affords greater
knowledge on a relevant issue than the jury possesses. State v. Macumber,
112 Ariz. 569, 570, 544 P.2d 1084, 1085 (1976).

¶18            Dr. Haber has a Ph.D. in experimental psychology from
Stanford, which in turn qualified him to teach experimental design at Yale,
the University of Illinois, and the University of Rochester for some twenty-
one years. Based on his education and experience, he founded his own
consulting business, through which he analyzes forensic science methods
and makes himself available to testify about their consistency with accepted
methods of scientific experimentation. He routinely conducts peer review
for academic journals in many scientific or forensic fields — including
firearm and toolmark analysis — regarding the experimental designs used
to support the conclusions reached. He has authored a paper for the
California Bar Association regarding “evidence in the criminal courts on
firearms and handgun identification.” Although he has been retained only
once to testify about the methods used in toolmark analysis, Dr. Haber has
studied and evaluated this issue for four years and “thoroughly
familiarized” himself with the research, publications, and methodology for
toolmark identification, including all publications from the Association for
Toolmark and Firearm Examiners.

¶19          With respect to experimental design, and a comparison of the
methods generally used by firearms examiners to the scientific method, Dr.
Haber is qualified as an expert.

                                       C.

¶20           Apart from Dr. Haber’s qualifications, his testimony would
not have been admissible unless it would have been helpful to the jury in
understanding the evidence. Ariz. R. Evid. 702(a). The State presented
Powell’s testimony that the indentations on shell casings demonstrated that
the Glock had fired all the shells, including those at the murder scene, and
the State argued that the toolmark comparisons demonstrated a match to
“a reasonable degree of scientific certainty.” Dr. Haber’s testimony would
have been helpful to the jury in understanding how the toolmark analysis
differed from general scientific methods and in evaluating the accuracy of
Powell’s conclusions regarding “scientific certainty.”


                                       6
                            STATE V. ROMERO
                            Opinion of the Court

¶21            The thrust of Dr. Haber’s testimony was that the methods
underlying toolmark analysis (here comparing indentations and other
marks on shell casings) are not based on the scientific method, but instead
reflect subjective determinations by the examiner conducting the analysis.
Haber would have explained that unlike experts who use other forms of
forensic analysis rooted in the scientific method, firearms examiners do not
follow an accepted sequential method for evaluating characteristics of fired
shell casings and comparing them to control subjects. By describing the
methods used by toolmark examiners, Dr. Haber’s testimony could have
helped the jury assess how much weight to place on Powell’s “scientific”
conclusion that the shell casings at the murder scene could only have been
fired from the Glock found by the police when they stopped Romero.

¶22            In affirming the exclusion of Dr. Haber’s testimony, the court
of appeals observed that Dr. Haber “could not describe the methods or
protocols of a toolmark analysis.” 236 Ariz. at 458 ¶ 25, 341 P.3d at 500.
This misconstrues the point of Dr. Haber’s testimony. One of his critiques
of the methodology used by firearms examiners is that they do not employ
identifiable, standardized protocols. Excluding testimony about the lack of
such protocols because the proffered expert witness cannot identify them
would transform a procedure’s weaknesses into a shield from criticism.
Such reasoning would undermine — rather than promote — Rule 702’s
purpose of helping the jury understand the evidence.

¶23           Moreover, the testimony would have been helpful even
though Dr. Haber had not himself performed a toolmark analysis and
would not have opined on the particular analysis performed by Powell.
Expert witnesses may helpfully educate the fact-finder about general
principles without considering the facts of a particular case. State v. Salazar-
Mercado, 234 Ariz. 590, 593 ¶ 10, 325 P.3d 996, 999 (2014) (holding that
“cold” expert testimony may be admitted under Rule 702). Dr. Haber’s lack
of experience in performing toolmark analyses and firearm identification
experiments might have affected the weight a juror would give his
testimony, but it did not bar its admission.

¶24            Dr. Haber’s testimony was intended to highlight that the
conclusions drawn by firearms examiners from toolmarks do not result
from the application of articulable standards and lack typical safeguards of
the scientific method such as independent verification by other examiners.
Thus, Dr. Haber’s testimony could have helped the jury to understand any

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                           STATE V. ROMERO
                           Opinion of the Court

deficiencies in the experimental design of toolmark analysis and to assess
any suggestion that such analysis was “scientific.” Cf. Salazar-Mercado, 234
Ariz. at 594 ¶ 15, 325 P.3d at 1000 (affirming admission of expert testimony
about general behavior patterns of child sexual abuse victims because it
“might have helped the jury to understand possible reasons for the delayed
and inconsistent reporting in this case”).

                                     D.

¶25           As an alternative grounds for excluding Dr. Haber’s
testimony, the trial court ruled that it would impermissibly amount to a
second Daubert hearing before the jury. Romero, 236 Ariz. at 457 ¶ 19, 341
P.3d at 499. Because the court of appeals affirmed the preclusion of Dr.
Haber’s testimony based on his lack of qualifications as a firearms
examiner, it did not address this alternative grounds. Id. at n.4.

¶26            The trial court reasoned that because it found Powell’s
methodology and conclusions sufficiently reliable to be admissible, the
defense could not present expert testimony at trial to challenge the prior
evidentiary ruling. We have rejected similar reasoning in interpreting
Arizona’s previous version of Rule 702. In Lehr, we held that a trial court,
after ruling based on a pretrial hearing that testimony by the State’s DNA
experts was admissible, erred by precluding cross-examination of the
experts at trial about protocols they had followed. 201 Ariz. at 517 ¶¶ 25-
29, 38 P.3d at 1180. Although the trial court had considered the testimony
to be elicited on cross-examination before ruling the State’s expert
testimony admissible, the defense was entitled to offer the same evidence
at trial through cross-examination to challenge that testimony. Id. The trial
court’s contrary reasoning, we noted, “fail[ed] to recognize that very often
the same proof used to establish admissibility also impacts weight and
credibility.” Id. ¶ 25. Consequently, blanket preclusion at trial of evidence
presented at a pretrial hearing “infringe[s] upon the role of the jury and
improperly insulate[s] the state’s evidence from critique.” Id. ¶ 29.

¶27           Our post-Daubert amendments to Rule 702 do not alter this
aspect of Lehr. Instead, we have recognized that a trial court’s admission of
disputed expert testimony leaves to the fact-finder the role of assessing its
weight and credibility. “Cross-examination, presentation of contrary
evidence, and careful instruction on the burden of proof are the traditional
and appropriate means of attacking shaky but admissible evidence.”

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                           STATE V. ROMERO
                           Opinion of the Court

Bernstein, 237 Ariz. at 231 ¶ 22, 349 P.3d at 205 (quoting Ariz. R. Evid. 702
cmt. (2012)).

¶28             Here, the trial court’s alternative ground for preclusion was
an error of law. Assuming that Powell’s methods and conclusions
regarding the purported “match” between the Glock and the shell casings
at the crime scene were sufficiently reliable to be admitted into evidence
(we declined review on this issue), it does not follow that the weight and
credibility of this evidence, once admitted, may not be challenged. See Lehr,
201 Ariz. at 517 ¶ 29, 38 P.3d at 1180 (noting jury’s province to determine
weight and credibility of expert testimony).

¶29           Our opinion, of course, does not suggest that a jury would
necessarily credit Dr. Haber’s testimony if it had been admitted. The State
could have challenged that testimony before the jury, including by noting
some of the points mentioned by the court of appeals, such as Dr. Haber’s
lack of experience in actually performing toolmark examinations or by
questioning whether standards for experimental design in other forensic
areas should apply to toolmarks. Such arguments, however, go to the
weight rather than the admissibility of Dr. Haber’s testimony.

¶30            The court’s exclusion of Dr. Haber’s testimony will not
require reversal of Romero’s conviction if the State can establish the error
was harmless beyond a reasonable doubt. The specially concurring opinion
concluded the error was harmless, 236 Ariz. at 469 ¶ 69, 341 P.3d at 511
(Eckerstrom, J., concurring), but the majority did not address this issue. We
accordingly remand to the court of appeals so that court may consider in
the first instance whether excluding Dr. Haber’s testimony was harmless.

                                    III.

¶31          We vacate paragraphs 19 through 32 of the opinion of the
court of appeals and remand to that court to determine if the error in
excluding Dr. Haber’s testimony was harmless.




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