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     BARBARA J. TIPLADY, ADMINISTRATRIX
       (ESTATE OF LINDA JABLONSKI) v.
           SAMUEL MARYLES ET AL.
                  (AC 35832)
                Gruendel, Prescott and Harper, Js.
        Argued January 15—officially released July 28, 2015

   (Appeal from Superior Court, judicial district of
 Stamford-Norwalk, Hon. Kevin Tierney, judge trial
 referee [motion to strike]; Genuario, J. [judgment])
  Angelo A. Ziotas, with whom were Peter M. Dreyer
and Michael P. Roffe, for the appellant (plaintiff).
  John B. Farley, with whom were Frederick J. Trotta,
Sr., and, on the brief, Hugh D. Hughes, for the appellees
(named defendant et al.).
  Eric J. Stockman, with whom, on the brief, was
Simon I. Allentuch, for the appellee (defendant Stam-
ford Health System, Inc.).
  Jennifer L. Cox and Jennifer A. Osowiecki field a
brief for the Connecticut Hospital Association as ami-
cus curiae.
                          Opinion

   GRUENDEL, J. In this medical malpractice action,
the plaintiff, Barbara J. Tiplady, administratrix of the
estate of Linda Jablonski, appeals from the judgment
of the trial court denying her motion to set aside the
jury verdict returned in favor of the defendants, Samuel
Maryles, Stamford Health Systems Inc. (Stamford Hos-
pital), Emergency Medicine Physicians of Fairfield
County, LLC, and Emergency Medicine Physicians Lim-
ited.1 On appeal, the plaintiff claims that the court
abused its discretion when it permitted Maryles, the
treating physician, to testify to expert opinions without
a proper foundation and then denied the plaintiff an
opportunity to cross-examine him on issues raised by
the elicited testimony.2 Specifically, the plaintiff argues
that the court improperly admitted expert testimony,
under the open door doctrine, that went beyond the
scope of earlier opinion testimony elicited by the plain-
tiff, and later improperly denied the plaintiff an opportu-
nity to challenge Maryles’ qualifications on cross-
examination. We agree and conclude that, under the
facts of this case, the court abused its discretion when
it admitted the challenged testimony, and that the error
was harmful. Accordingly, we reverse the judgment of
the trial court.
   The following facts and procedural history reason-
ably could have been found at trial. On November 15,
2004, Jablonski presented to the emergency department
at Stamford Hospital complaining of headaches and
nausea. Jablonski first was examined by a triage nurse,
who reported that she had experienced headaches for
the past four or five days and had been ‘‘vomiting since
last week.’’ Jablonski then was examined and treated
by Maryles, a physician specializing in emergency medi-
cine. Maryles reported that Jablonski was ‘‘a [forty-two]
year old female who presents complaining of vomiting
for the last couple of days on and off associated with
atypical migraine type headache for her that started
today.’’ His report also noted that Jablonski had a his-
tory of migraines and had previously been prescribed
Imitrex, a drug used to treat migraine headaches. Mar-
yles then performed a medical evaluation of Jablonski.
   At 7:10 p.m., Maryles began treatment of Jablonski
by providing her with intravenous saline fluid, Pepsid,
and Reglan. The purpose of the saline fluid was to
address the loss in fluids, resulting from the Jablonski’s
vomiting. Pepsid, an antacid, was given to address her
nausea. Reglan was provided to treat her headache pain.
At 8 p.m., a nurse evaluated Jablonski, who stated that
her headache persisted, describing the pain as an eight
on a ten point scale. Maryles then prescribed Toradol,
an anti-inflammatory medication, to address Jablonski’s
headache. At 8:56 p.m., with the headache continuing
to persist, Maryles prescribed Vicodin, which was effec-
tive in reducing the pain. At 9:56 p.m., Jablonski’s condi-
tion had improved and she was discharged from the
emergency room. Maryles reported a final diagnosis of
hepatitis and migraine headache. He requested lab tests
regarding the possibility of hepatitis and instructed
Jablonski to follow up with her physician in the next
two or three days.
   The following day, Jablonski was taken by the police
to Bridgeport Hospital after she was found driving in
the wrong direction on a highway exit ramp. When the
police found her, she was confused and disoriented.
Doctors at Bridgeport Hospital determined that she was
suffering from herpes simplex encephalitis, a viral infec-
tion of the brain that causes swelling that can result in
coma or death. Common symptoms of the infection are
headache, fever, weakness on one side of the body,
aphasia, nausea, and vomiting; however, not all symp-
toms are present in every patient. The viral infection
tends to run its course between three days and a week
from the initial presentation of symptoms. The medical
professionals at Bridgeport Hospital, upon reaching
their diagnosis, treated Jablonski with a drug called
Acyclovir. She failed to respond to treatment and suc-
cumbed to the disease several days later. An autopsy
later confirmed the cause of death as herpes simplex
encephalitis.
  After Jablonski’s death, the plaintiff, her mother, filed
the present medical malpractice action, in her capacity
as administratrix of the estate of her daughter, against
the defendants and Stamford Hospital. The plaintiff’s
complaint alleged that Maryles and Stamford Hospital
personnel negligently failed to diagnose and treat
Jablonski’s condition. The complaint further alleged
that the failure to diagnose and treat her condition
ultimately led to her death.
   Prior to trial, the defendants filed a motion in limine,
seeking to preclude from evidence a consent agreement
and order entered into by Maryles with the New York
Department of Health, as well as evidence that Maryles
twice previously had failed the emergency medicine
board examination. The consent agreement and order
related to a 2007 investigation by the New York State
Department of Health’s Office of Professional Medical
Conduct (department). As a result of that investigation,
the department brought seven counts of professional
misconduct against Maryles, including ‘‘[failure] to
maintain a record for each patient [that] accurately
reflects the care and treatment of the patient’’ and ‘‘prac-
ticing medicine with negligence on more than one occa-
sion.’’ The court granted the motion in limine on the
ground that the evidence was more prejudicial than
probative.3 At the same time, the court clarified that
the order was preliminary and that the evidence could
become admissible if the defendants offered evidence
regarding Maryles’ qualifications or habit. In reaching
that ruling, the court emphasized that Maryles had not
been offered by either party as an expert witness.
  During her case-in-chief, the plaintiff called Maryles
to testify. The plaintiff did not disclose Maryles as an
expert witness, nor was a foundation laid establishing
his credentials. Notwithstanding this, the plaintiff asked
a question that elicited medical opinion, which was
answered without objection. The plaintiff asked Mar-
yles, ‘‘[y]ou and I are in agreement then, an atypical
migraine headache needed to be worked up with a CAT
scan and a lumbar puncture. Right?’’ Maryles agreed
that this was the appropriate treatment for an atypical
headache. The plaintiff’s counsel then stated: ‘‘Now, I’m
not asking you that as an expert. I’m asking you as a
party.’’ At the conclusion of the plaintiff’s direct exami-
nation, the defendants stated that they would reserve
their cross-examination questions for their case-in-
chief.
   On September 19, 2012, the defendants called Maryles
to testify. The defendants’ counsel began with a series
of questions related to his professional background.
Maryles was asked where he went to high school and
college; he was asked if he graduated from college and
the types of courses that were included in his ‘‘pre-med
studies.’’ The defendants’ counsel started to ask the
following question before he was interrupted by the
court: ‘‘And then following your graduation from [your
undergraduate university], sir . . . .’’ The court inter-
rupted the examination and excused the jury from the
courtroom. The court then explained that, ‘‘I was clear
that if you put the doctor’s credentials in issue that the
plaintiff would then be able to cross-examine more
thoroughly. The only conclusion that I could draw [from
the defendants’ counsel’s questioning] was that you
were confused as to my ruling. I want everybody to be
clear what my ruling was. And that if you put the doc-
tor’s credentials at issue, then I’m going to allow the
consent decree to come in.’’ The court later stated:
‘‘Maybe you weren’t going any further, but you were
going down a road which in my opinion would have
resulted in me having to let in evidence that I have
already indicated more times than I want to that I think
is prejudicial and not particularly probative but the
plaintiff would have that right.’’ The court then ruled
that the defendants’ counsel had not opened the door
to allow evidence of Maryles’ New York consent decree.
   Before proceeding, the court provided the plaintiff’s
counsel with an opportunity to be heard. The plaintiff’s
counsel replied with the following: ‘‘[The defendants’
counsel] was starting to elicit a clear list of qualifica-
tions and credentials that would have allowed Your
Honor to do what I believe is fair and right. I’m sitting
here with my head down, [my cocounsel] is writing
notes trying to keep . . . Your Honor from doing what
you just did. You injected yourself as cocounsel for the
defense. There’s no ambiguity. . . . We were talking
about something that you were, absolutely, one hundred
percent clear on. . . . So for this court to pull us up
to sidebar when this witness is in the middle of allowing
the plaintiff to get a fair trial, I object.’’ The plaintiff’s
counsel then moved to strike the prior testimony and
the court denied the motion on the basis that the ques-
tions only covered Maryles’ high school and college
education and ‘‘it is common knowledge that doctors
need to go to college [and] need to go to high school.’’
   The jury returned and the defendants’ direct examina-
tion of Maryles continued. During the examination, the
defendants’ counsel asked several questions that elic-
ited medical opinion testimony. Although the plaintiff’s
counsel objected on the basis that Maryles had not
been offered as an expert, the court overruled those
objections on the ground that the plaintiff’s counsel
had opened the door when he elicited medical opinion
testimony during the plaintiff’s case-in-chief. Maryles
was asked by the defendants’ counsel, over the plain-
tiff’s objection, whether it was important, when he is
assessing someone with a headache complaint, to
observe: (1) whether the head is normal-cephalic and
atraumatic, (2) the extraoccular eye movements, (3)
the cranial nerves, and (4) whether the patient’s eyes
are closed. Maryles answered affirmatively, stating that
it was important to consider each of the observations.
He then explained why each assessment was important
in properly diagnosing a patient who presents with a
headache.
   The defendants’ counsel then asked Maryles other
questions eliciting expert opinions. Counsel asked:
‘‘When a patient complains of an atypical, all one word,
headache, are there things that are done to manage that
complaint.’’ Maryles testified that ‘‘after doing a proper
physical examination, you generally do some blood
tests, and then potentially a CAT scan and a lumbar
puncture.’’ The defendants’ counsel then asked: ‘‘What
are the things you are alert for when a patient complains
of [an] atypical headache?’’ After the court overruled
an objection from the plaintiff’s counsel, Maryles stated
that ‘‘[a] patient . . . with an atypical headache is at
risk for things like infection of the brain as well as
bleeding, as well as things like tumors and masses.’’
Maryles then was asked what the proper method was
for treating a patient with a typical headache. Maryles
testified that he would review the patient’s history,
‘‘making sure that this is their usual headache; that this
is not different than the headache they normally have
. . . .’’ Finally, the defendants’ counsel asked about
a notation from the medical report from Jablonski’s
admission to the Stamford Hospital emergency room.
The notation stated that she suffered from ‘‘atypical’’
headache. Maryles responded that it was his belief that
the notation was the result of a typographical error,
and should be read as ‘‘a typical’’ headache.
   At the conclusion of trial, the jury returned a verdict
in favor of the defendants. Through its responses to
interrogatories, the jury found that the plaintiff had
failed to prove that Maryles had deviated from the stan-
dard of care.4
  Following the jury verdict, the plaintiff filed a motion
to set aside the verdict and for a new trial. On June 12,
2013, in its memorandum of decision, the court denied
both motions, and the plaintiff appealed.
                             I
   The plaintiff claims that the court abused its discre-
tion when it improperly allowed the defendants to elicit
expert testimony from Maryles. At trial, the court ruled
that, although he had not been offered as an expert,
Maryles had provided expert opinion testimony under
the plaintiff’s examination and that, under the open the
door doctrine, it would allow the defendants to elicit
similar testimony within the same scope. The plaintiff
argues that Maryles’ subsequent testimony under the
defendants’ direct examination went beyond the scope
of the initial offer, and thus the admission of such testi-
mony was an abuse of the court’s discretion. Addition-
ally, the plaintiff argues that the court further
compounded this error when it precluded the plaintiff
from an opportunity to fully cross-examine Maryles
regarding his credentials. We agree.
   We begin by setting forth the applicable standard of
review. ‘‘It is well established that [t]he trial court’s
ruling on evidentiary matters will be overturned only
upon a showing of a clear abuse of the court’s discre-
tion.’’ (Internal quotation marks omitted.) Prentice v.
Dalco Electric, Inc., 280 Conn. 336, 342, 907 A.2d 1204
(2006), cert. denied, 549 U.S. 1266, 127 S. Ct. 1494,
167 L. Ed. 2d 230 (2007). ‘‘[E]ven when a trial court’s
evidentiary ruling is deemed to be improper . . . we
[still] must determine whether that ruling was so harm-
ful as to require a new trial. . . . In other words, an
evidentiary ruling will result in a new trial only if the
ruling was both wrong and harmful. . . . [T]he stan-
dard in a civil case for determining whether an improper
ruling was harmful is whether the . . . ruling [likely]
would [have] affect[ed] the result.’’ (Emphasis omitted;
internal quotation marks omitted.) Id., 358. In assessing
harm, we consider whether the ‘‘erroneously admitted
evidence . . . [may have] affected the jury’s percep-
tion of the remaining evidence.’’ Swenson v. Sawoska,
215 Conn. 148, 153, 575 A.2d 206 (1990). We now con-
sider each of the plaintiff’s claims of evidentiary impro-
priety and then consider whether the resulting error
was harmful.
                            A
  Expert testimony is admissible if (1) the witness is
qualified as an expert and (2) the testimony assists the
ing a fact at issue. See Conn. Code Evid. § 7-2, commen-
tary. An expert’s testimony is admissible only when the
witness has ‘‘special skill or knowledge, beyond the ken
of the average juror, on the particular subject at issue
. . . .’’ State v. George, 194 Conn. 361, 373, 481 A.2d
1068 (1984), cert. denied, 469 U.S. 1191, 105 S. Ct. 963,
83 L. Ed. 2d 968 (1985). The sufficiency of the expert’s
qualifications is a preliminary question for the court.
Blanchard v. Bridgeport, 190 Conn. 798, 808, 463 A.2d
553 (1983). Before expert testimony may be admitted,
the court must determine whether the scope of the
expert’s knowledge and experience qualifies him to ren-
der an expert opinion. See Oborski v. New Haven Gas
Co., 151 Conn. 274, 280, 197 A.2d 73 (1964).
   Although evidence may be otherwise inadmissible,
‘‘a party who delves into a particular subject during the
examination of a witness cannot object if the opposing
party later questions the witness on the same subject.
. . . The party who initiates discussion on the issue is
said to have ‘opened the door’ to rebuttal by the oppos-
ing party. Even though the rebuttal evidence would
ordinarily be inadmissible on other grounds, the court
may, in its discretion, allow it where the party initiating
inquiry has made unfair use of the evidence.’’ (Citations
omitted.) State v. Graham, 200 Conn. 9, 13, 509 A.2d
493 (1986). The purpose of this doctrine is to ‘‘prevent
a [party] from successfully excluding inadmissible . . .
evidence and then selectively introducing pieces of this
evidence for his own advantage, without allowing [the
opposing party] to place the evidence in its proper con-
text.’’ (Internal quotation marks omitted.) Id.
   Under the open the door doctrine, a court must ‘‘con-
sider whether the circumstances of the case warrant
further inquiry into the subject matter, and should per-
mit [the evidence] . . . to the extent necessary to
remove any unfair prejudice which might otherwise
have ensued from the original evidence.’’ (Internal quo-
tation marks omitted.) Somers v. LeVasseur, 230 Conn.
560, 566, 645 A.2d 993 (1994). Stated differently, the
opposing party is allowed to place the initial evidence
in its proper context. See State v. Glenn, 194 Conn. 483,
498–99, 481 A.2d 741 (1984). ‘‘Such a decision, of course,
rests within the discretion of the trial court.’’ Somers
v. LeVasseur, supra, 566.
  In the present case, the plaintiff’s direct examination
of Maryles elicited expert testimony regarding the stan-
dard of care for a patient complaining of an atypical
headache. Thus, under the open the door doctrine, it
would have been proper to allow the defendants’ coun-
sel to elicit testimony regarding the appropriate stan-
dard of care. As the presentation of Jablonski’s
headache was a key issue at trial, it would have been
appropriate for Maryles to clarify that although an atypi-
cal headache required a CAT scan and a lumbar punc-
ture, a traditional migraine headache did not. It also
would have been appropriate for Maryles to testify to
the standard of care for a patient complaining of a
typical migraine headache.
  Our review of the transcript reveals that the defen-
dants’ examination of Maryles was not limited to the
extent necessary to place his earlier testimony in con-
text. Over the plaintiff’s objection, the defendants’ coun-
sel solicited, and Maryles offered, medical opinions that
went beyond the standard of care issues raised by
the plaintiff.5
   The following examples highlight the ways in which
Maryles offered medical opinion testimony. He testified
regarding the various ailments that he is ‘‘alert for when
a person complains of an atypical headache.’’ He stated
that ‘‘a patient . . . with an atypical headache is at risk
for things like infections of the brain as well as bleeding,
as well as things like tumors and masses. So, the workup
is to essentially rule out those possibilities.’’ Maryles
further explained the importance of several assess-
ments that are performed during the treatment of a
headache. These assessments included determining
whether the patient’s head was normal-cephalic and
atraumatic. To this point, Maryles stated that ‘‘then you
would know whether they’d suffered any trauma and
. . . whether their head was of normal shape.’’ He
explained why it was critical to assess the patient’s
extraoccular eye movement, stating: ‘‘If their extraoccu-
lar movements are intact then you know that they’re not
suffering any cranial nerve abnormalities.’’ Additionally,
he testified that it was important to assess the patient’s
cranial nerves, stating: ‘‘If the cranial nerves are intact,
they’re less likely to have an issue going on which would
affect them, such as inflammation or mass.’’ Lastly,
Maryles stated that it was important to assess whether
the patient had photophobia, because ‘‘certain maladies
such as migraines can be worsened by lights.’’ All of
these opinions went beyond the scope of testimony
elicited by the plaintiff and required Maryles to rely on
his professional experience and expertise.
   Moreover, Maryles’ expert testimony went beyond
the issue of the standard of care raised by the plaintiff,
namely, what an emergency room physician is required
to do under the circumstances. Specifically, the testi-
mony extended to what Maryles does and looks for
when treating a patient with headaches. Standard of
care in the medical malpractice context is defined as
the ‘‘degree of skill and learning commonly applied
under . . . the circumstances in the community by the
average prudent reputable member of the profession
. . . .’’ (Internal quotation marks omitted.) Gold v.
Greenwich Hospital Assn., 262 Conn. 248, 254, 811 A.2d
1266 (2002). Breach in a medical malpractice case is
defined as a deviation from the professional standard.
Id. Maryles was asked by the defendants’ counsel:
‘‘What are the things you are alert for when a patient
complains of an atypical headache?’’ He later was
asked: ‘‘And Doctor, the same question with regard to
a patient complaining of a space typical headache.’’
Maryles’ responses did not explain the appropriate stan-
dard of the profession, but rather explained what his
particular knowledge, understanding, and practice is
when treating patients with headaches. Trimel v. Law-
rence & Memorial Hospital Rehabilitation Center, 61
Conn. App. 353, 358, 764 A.2d 203 (medical malpractice
presupposes ‘‘the failure to exercise [the] requisite med-
ical skill’’ [internal quotation marks omitted]), appeal
dismissed, 258 Conn. 711, 784 A.2d 889 (2001). Maryles’
testimony regarding the importance of each step of his
treatment, as well as his knowledge of the potential
underlying causes of a headache, support the defen-
dants’ position that Maryles had not deviated from the
standard of care because he knew how to properly treat
both typical and atypical headaches.
   In concluding that the defendants’ direct examination
of Maryles elicited testimony that exceeded the scope
of the plaintiff’s examination, we follow the established
principle that ‘‘[t]he doctrine of opening the door can-
not, of course, be subverted into a rule for injection of
prejudice. . . . The trial court must carefully consider
whether the circumstances of the case warrant further
inquiry into the subject matter, and should permit it
only to the extent necessary to remove any unfair prej-
udice which might otherwise have ensued from the
original evidence.’’ (Citations omitted; emphasis
added; internal quotation marks omitted.) State v. Gra-
ham, supra, 200 Conn. 13–14. When the defendants’
counsel elicited Maryles’ opinions beyond the scope of
the plaintiff’s initial offer, the plaintiff objected and the
objection was overruled. In overruling the objection,
the court permitted the defendants to present expert
testimony without first laying a foundation regarding
the scope of Maryles’ expertise. A party who wishes to
offer expert testimony must disclose the expert prior to
trial and establish their qualifications and skill through
foundational evidence. See Practice Book § 13-4 (requir-
ing disclosure of each person who may testify as expert
at trial); Weaver v. McKnight, 313 Conn. 393, 405–406,
97 A.3d 920 (2014) (offering party must establish expert
has special skill or knowledge directly applicable to
matter that would be helpful to jury in considering
issues). Maryles’ testimony was therefore not admissi-
ble as expert testimony and, alternatively, was not
admissible under the open the door doctrine. Accord-
ingly, we conclude that the court abused its discretion
in admitting the testimony.
                             B
  The plaintiff next claims that the court abused its
discretion when it barred cross-examination of Maryles’
credentials. We agree.
  The court’s impropriety regarding the extent to which
it permitted the defendants’ counsel to elicit extensive
opinion testimony was compounded when it precluded
the plaintiff’s counsel from challenging Maryles’ qualifi-
cations and experience on cross-examination. On cross-
examination, the plaintiff’s counsel attempted to ask
Maryles ‘‘in your prior job, you were not let go under
good circumstances, were you?’’ The defendants’ coun-
sel objected and the court sustained the objection. After
excusing the jury, the court heard argument from both
sides. The plaintiff’s counsel asserted that he should
be permitted to ask Maryles’ questions that challenged
his credibility as a witness. The defendants’ counsel
argued that the motion in limine regarding the doctor’s
consent agreement precluded such questions. The court
sustained the objection, stating: ‘‘I do not want any
further questions in front of the jury that are designed
to elicit either the consent decree or the circumstances
underlying the consent decree.’’6
   It is well established that ‘‘[c]ross-examination is an
indispensable means of eliciting facts that may raise
questions about the credibility of witnesses and, as a
substantial legal right, it may not be abrogated or
abridged at the discretion of the court to the prejudice
of the party conducting that cross-examination.’’ Hayes
v. Manchester Memorial Hospital, 38 Conn. App. 471,
474, 661 A.2d 123, cert. denied, 235 Conn. 922, 666 A.2d
1185 (1995). ‘‘One of the proper purposes of cross-exam-
ination of an expert is to test the expert’s qualifications
and credibility . . . .’’ Richmond v. Longo, 27 Conn.
App. 30, 38, 604 A.2d 374, cert. denied, 222 Conn. 902,
606 A.2d 1328 (1992). ‘‘[Q]uestions regarding the
expert’s skill and qualifications go to the expert’s credi-
bility.’’ Id.
   As Maryles’ testimony constituted expert opinion, his
testimony, in response to the defendants’ counsel’s
direct examination, placed Maryles’ qualifications and
experience at issue, and the plaintiff should have been
permitted an opportunity to challenge his testimony
during cross-examination. In other words, the door
must swing open in both directions. Accordingly, we
conclude that the court also abused its discretion when
it denied the plaintiff an opportunity to cross-examine
Maryles regarding his qualifications.
                            C
   We now consider whether these improprieties consti-
tute reversible error. At closing argument, the defen-
dants’ counsel used Maryles’ opinion testimony as the
basis for his defense against the claim that he had devi-
ated from the standard of care. The defendants’ counsel
argued: ‘‘Maryles did testify what he would do if a head-
ache was atypical, offered by the plaintiff’s that very
first day. Atypical: Well, you do a lumbar puncture and
a CT scan. You had the chance to see Dr. Maryles.
You’ve assessed that man. You heard him speak. You
saw him on the stand under very hostile circumstances.
He stands straight up, ladies and gentlemen. He does
not dodge. He tells you exactly how he feels he treats
patients. And if it’s a typical with a response to medi-
cation the patient doesn’t get a CT and a lumbar. If
it’s atypical, she does.’’ (Emphasis added.) The essence
of this argument was that Maryles had not deviated
from the standard of care because he understood how
to properly treat a patient with a headache. On this
basis, the defendants implored the jury to conclude that
Jablonski did not present with atypical headaches on
the day in question because, if she had, Maryles would
have properly diagnosed and treated it. This argument
relied on the credibility of Maryles’ opinion testimony.
He had testified that he knew the appropriate standard
of care for patients with typical headaches, as well as
the standard of care for patients with atypical head-
aches. He had testified that he knew the various medical
conditions that can cause a headache. He had also testi-
fied about each assessment that was performed and
explained its importance in diagnosing the patient. This
testimony was not merely cumulative of other evidence
presented in this case. See Swenson v. Sawoska, supra,
215 Conn. 155 (erroneously admitted evidence, if cumu-
lative of other evidence, does not constitute harmful
error). As Maryles’ expert testimony formed the basis
of the defendants’ defense to the claim that Maryles
committed medical malpractice, we conclude that the
improper admission of that testimony was harmful.7
   Moreover, Maryles’ expert testimony likely affected
the jury’s evaluation of the remaining evidence pre-
sented at trial, specifically the medical report from
Jablonski’s admission to the Stamford Hospital emer-
gency room. The medical report served as the only
evidence of Jablonski’s condition in the emergency
room, as well as the medical treatment she received.
At trial, the plaintiff argued that the ‘‘atypical headache’’
notation was probative evidence that Maryles had
breached the standard of care when he failed to perform
a CAT scan and a lumbar puncture. The defendants
argued that the notation was a typographical error. As
Maryles had dictated the contents of that medical
report, his expert testimony, without a full cross-exami-
nation, colored the jury’s perception on this critical
issue of fact. If the jury determined that Maryles was
credible, then it would be more likely to credit his
explanation that the notation was a typographical error.
If, on the other hand, the jury determined that Maryles
was not credible, then it would be more likely to con-
clude that, faced with a patient with an atypical head-
ache, Maryles had deviated from the standard of care
by not performing a CAT scan and lumbar puncture.
Thus, we conclude that the improper admission of Mar-
yles’ expert testimony that was beyond the scope of
the testimony originally elicited by the plaintiff, and the
court’s subsequent denial of proper cross-examination
regarding Maryles’ qualifications, likely affected the
result of the trial and, therefore, constituted harmful
error. Accordingly, the case must be remanded for a
new trial.
                             II
                             A
   Because we concluded that the case is to be
remanded for a new trial, it is appropriate for us to
address certain issues, raised by the plaintiff, that are
likely to recur on retrial. See Sullivan v. Metro-North
Commuter Railroad Co., 292 Conn. 150, 164, 971 A.2d
676 (2009). First, the plaintiff claims that the trial court
erred in deciding, as a matter of law, that Stamford
Hospital could not be liable for the torts of its apparent
agents. We decline, however, to reach the merits of this
claim for the reasons we set forth.
   The following relevant procedural history can be
found in the court’s memorandum of decision on the
plaintiff’s motions to set aside the verdict and for a new
trial. ‘‘By way of background, in count three of the
revised complaint dated May 28, 2012, the plaintiff
alleged that Dr. Maryles was acting as the actual or
apparent agent of Stamford Hospital. It is undisputed
that Dr. Maryles was the employee of the defendant
Emergency Medicine Physicians of Fairfield County,
LLC (EMP). It was also undisputed that Stamford Hospi-
tal contracted with EMP to provide emergency depart-
ment physicians at Stamford Hospital. The parties had
previously filed cross motions for summary judgment
on the issue of apparent agency but agreed to reserve
the issue of apparent agency for the trial judge.’’ Prior
to the start of evidence, the court granted Stamford
Hospital’s motion in limine to preclude evidence con-
cerning apparent agency. ‘‘Since apparent agency deals
with vicarious liability and a jury found that the defen-
dant Dr. Maryles was not liable to the plaintiff, the issue
of apparent agency has become moot in the case at bar
. . . . Nonetheless, because of the importance of the
issue . . . this court needs to set forth its ruling and
rationale.’’ The court then analyzed the case law and
ruled ‘‘based upon L & V Contractors, [LLC v. Heritage
Warranty Ins. Risk Retention Group, Inc., 136 Conn.
App. 662, 669–70, 47 A.3d 887 (2012)] the doctrine of
apparent agency would not be available to the plaintiff
in this case in her effort to hold the Stamford Hospital
liable for alleged tortious conduct of the defendant
Dr. Maryles.’’8
  ‘‘Mootness implicates a court’s subject matter juris-
diction . . . . [I]t is required, among other things, that
there be an actual controversy between or among the
parties . . . .’’ (Citation omitted; internal quotation
marks omitted.) State v. T.D., 286 Conn. 353, 361, 944
A.2d 288 (2008). ‘‘If the trial court issues a decision on
the merits of a case over which it lacks subject matter
jurisdiction, the decision constitutes an advisory opin-
ion. . . . Such an opinion is not a judgment and is
not binding on anyone.’’ (Citations omitted; internal
quotation marks omitted.) PHH Mortgage Corp. v. Cam-
eron, 130 Conn. App. 238, 242, 22 A.3d 1282 (2011). In
the present case, the jury’s verdict barred the vicarious
liability claim against Stamford Hospital. Thus, the
court’s analysis of the application of apparent authority
constituted an advisory opinion and is not reviewable
on appeal because the underlying issue is moot. Accord-
ingly, we do not reach the merits of this claim.
                             B
   The plaintiff also claims that the court erred when
it struck certain paragraphs of her complaint alleging
that Stamford Hospital had a nondelegable duty to the
patients who are treated in its emergency room. The
plaintiff argues that certain regulations impose a duty
on hospitals to provide adequate emergency room care
to patients and that this duty is nondelegable. Stamford
Hospital argues that Connecticut has never recognized
such a claim. We agree with Stamford Hospital.
   The following procedural history is relevant to our
resolution of the plaintiff’s claim. Prior to trial, Stamford
Hospital filed a motion to strike paragraphs 15, 16, and
17 of the plaintiff’s complaint on the basis that the
paragraphs alleged an unrecognized nondelegable duty
and therefore failed to state a cause of action.9 On June
25, 2010, the court, Hon. Kevin Tierney, judge trial
referee, granted the motion on the basis that the state
‘‘does not recognize a claim based on nondelegable duty
against a Connecticut hospital for the negligence of
physicians employed by another nonhospital entity as
emergency room physicians staffing that hospital’s
emergency room.’’
   ‘‘The standard of review in an appeal challenging
a trial court’s granting of a motion to strike is well
established. A motion to strike challenges the legal suffi-
ciency of a pleading, and, consequently, requires no
factual findings by the trial court. As a result, our review
of the court’s ruling is plenary. . . . We take the facts
to be those alleged in the [pleading] that has been
stricken and we construe the [pleading] in the manner
most favorable to sustaining its legal sufficiency.’’
(Internal quotation marks omitted.) Himmelstein v.
Windsor, 116 Conn. App. 28, 33, 974 A.2d 820 (2009),
aff’d, 304 Conn. 298, 39 A.3d 1065 (2012).
  ‘‘It is well established that, [u]nder the general rule,
an employer is not liable for the negligence of its inde-
pendent contractors. . . . One exception to this gen-
eral rule, however, is [when] the owner or occupier of
premises owes invitees a nondelegable duty to exercise
ordinary care for the safety of such persons. . . . Non-
delegable duties generally are imposed, most often by
statute, contract or common law, in recognition of the
policy judgment that certain obligations are of such
importance that employers should not be able to escape
liability merely by hiring others to perform them. . . .
In such circumstances, the nondelegable duty doctrine
means that [the employer] may contract out the perfor-
mance of [its] nondelegable duty, but may not contract
out [its] ultimate legal responsibility. . . . Thus, the
nondelegable duty doctrine creates a form of vicarious
liability, whereby the employer remains vicariously lia-
ble for the negligence of its independent contractors
in their performance of the employer’s nondelegable
duty.’’ (Citations omitted; emphasis omitted; internal
quotation marks omitted.) Machado v. Hartford, 292
Conn. 364, 371–72, 972 A.2d 724 (2009).
  In arguing the existence of a nondelegable duty in
the present case, the plaintiff relies on two regulations,
one state and one federal, that require hospitals to pro-
vide emergency care to the public. The state regulation;
Regs. Conn. State Agencies § 19-13-D3 (j) (2); requires
that ‘‘[e]ach general hospital shall be organized in such
a way as to provide adequate care for persons with
acute emergencies at all hours.’’ The plaintiff argues
that this requirement establishes a hospital’s nondelega-
ble duty for malpractice by independent physicians
working in its emergency room. We are not persuaded.
Subsection (j) (3) of § 19-13-D3 states that ‘‘[i]n a city
or town with two or more hospitals, the operation by
one such hospital, under a mutual agreement, accept-
able to the Connecticut Department of Health, of an
emergency room twenty-four hours a day shall be con-
sidered satisfactory compliance with this section
. . . .’’ Subsections (j) (2) and (j) (3) of § 19-13-D3,
when read in context, state clearly that one hospital
can contract its duty to provide emergency room care.
Thus, Stamford Hospital’s duty is delegable and the
regulation does not support the plaintiff’s claim.10
   The federal regulation cited by the plaintiff, 42 C.F.R.
§ 482.12, requires that hospitals maintain a governing
body that is legally responsible for the conduct of the
hospital. Subsection (e) of § 482.12 states that the gov-
erning body ‘‘must be responsible for services furnished
in the hospital whether or not they are furnished under
contracts. . . . (1) The governing body must ensure
that services performed under a contract are provided
in a safe and effective manner.’’ The plaintiff urges
us to construe this regulation as imposing a duty on
Stamford Hospital to ensure that independently con-
tracted physicians do not conduct malpractice while
treating patients in its emergency room. We disagree.
  First, the purpose of 42 C.F.R. § 482 is to ‘‘serve as a
basis of survey activities for the purpose of determining
whether a hospital qualifies for a provider agreement
under Medicare and Medicaid.’’ 42 C.F.R. § 482.1 (b).
Given this stated purpose, it is unclear how the federal
regulation supports the plaintiff’s proposition.
  Second, the plaintiff concedes that Connecticut has
not previously recognized a nondelegable duty in the
context of a hospital and an independent contractor
physician. Neither of the regulations relied upon by the
plaintiff creates such a duty under these facts, and the
plaintiff has directed us to no other statutory or com-
mon-law authority imposing such a duty on a hospital.
Our review of the applicable case law also revealed no
such recognized species of liability. Accordingly, the
court properly struck the paragraphs alleging that Stam-
ford Hospital had a nondelegable duty to Jablonski.
  We have reviewed the remainder of the plaintiff’s
claims of error and do not consider them likely to arise
on retrial. State v. Jones, 234 Conn. 324, 351, 662 A.2d
1199 (1995). The error already found in the judgment
make it unnecessary for us to identify and discuss these
claims further.
  The judgment is reversed and the case is remanded
for a new trial.
      In this opinion the other judges concurred.
  1
      In this opinion, we refer to Maryles and his employers, Emergency Medi-
cine Physicians of Fairfield County, LLC, and Emergency Medicine Physi-
cians Limited, collectively as the defendants. We refer to Stamford Hospital
as such.
    2
      The plaintiff also claims that the court improperly: (1) instructed the
jury to consider Maryles’ testimony in the same manner as any other expert,
(2) denied her request to strike the testimony of the defendants’ expert, (3)
concluded that Stamford Hospital did not owe a nondelegable duty to its
emergency room patients, and (4) concluded, as a matter of law, that Stam-
ford Hospital could not be liable for the torts of its apparent agents. Because
we agree with the plaintiff’s evidentiary claim, which is dispositive, we do
not reach the merits of the plaintiff’s first and second additional claims. To
the extent necessary, we address the plaintiff’s third and fourth claims in
part II of this opinion.
    3
      We note that the court’s decision to grant the motion in limine is not
the subject of this appeal.
    4
      The jury’s interrogatory responses are as follows:
    ‘‘Interrogatory 1: Did the plaintiff prove by a preponderance of the evi-
dence, the standard of care applicable to [Maryles]? Yes.
    ‘‘Interrogatory 2: Did the plaintiff prove by a preponderance of the evi-
dence, that [Maryles] deviated from the accepted standard of care as
alleged? No.’’
    5
      The plaintiff’s counsel made a timely objection to Maryles’ expert testi-
mony. When the first question eliciting expert opinion testimony was asked,
he said: ‘‘Objection, Your Honor. It’s beyond the scope now of the initial
examination. We’re getting into opinions that were not elicited.’’ The court
overruled this objection and allowed the testimony.
    6
      Prior to making its ruling, the court ordered the plaintiff’s counsel to
divulge the questions he planned to ask Maryles on cross-examination. With
Maryles and the jury outside of the courtroom, but in the presence of
opposing counsel, the plaintiff’s counsel was required to explain to the court
the questions he planned to ask regarding Maryles’ credibility, qualifications,
and employment status.
    7
      Furthermore, the court’s charge to the jury did nothing to cure the harm.
At the conclusion of trial, the court instructed the jury to evaluate Maryles’
testimony using the ‘‘same criteria . . . [used] to evaluate the opinions
and credibility of the expert witnesses in this matter.’’ The court stated that
‘‘expert witnesses are people who have knowledge beyond that of an ordi-
nary person. . . . [And that] [b]ecause of [their] expertise in whatever field
they happen to be in, expert witnesses are allowed to give their opinion.’’
This instruction had the reasonable likelihood of misleading the jury because
it requested the jury to evaluate Maryles’ credibility without any foundational
evidence regarding his qualifications. It also had the potential to elevate
Maryles’ testimony to that of a qualified expert. State v. George, supra, 194
Conn. 373 (noting danger that ‘‘[a] gloss of expertise, like a bit of frosting’’
will improperly influence jury’s fact finding function).
  8
    We note that our Supreme Court, in another case, recently granted
certification on this issue. See Cefaratti v. Aranow, 315 Conn. 919, 107 A.3d
960 (2015).
  9
    No party challenges the court’s determination that these paragraphs
purported to state a distinct cause of action against Stamford Hospital and,
therefore, were properly the subject of a motion to strike.
  10
     We do not purport to decide whether a hospital in a town or a city that
does not have a second hospital has a nondelegable duty to provide adequate
care for persons with acute emergencies at all hours.
