22CA0477 Peo v Bannan 03-26-2026
COLORADO COURT OF APPEALS
Court of Appeals No. 22CA0477 Boulder County District Court No. 19CR2042 Honorable Norma A. Sierra, Judge
The People of the State of Colorado,
Plaintiff-Appellee,
v.
Justin Lewis Bannan,
Defendant-Appellant.
JUDGMENT AFFIRMED
Division V Opinion by JUDGE WELLING Grove and Johnson, JJ., concur
NOT PUBLISHED PURSUANT TO C.A.R. 35(e) Announced March 26, 2026
Philip J. Weiser, Attorney General, Grant R. Fevurly, Senior Assistant Attorney General, Denver, Colorado, for Plaintiff-Appellee
The Noble Law Firm, LLC, Antony Noble, Jennifer Tuttle, Lakewood, Colorado, for Defendant-Appellant ¶1 Justin Lewis Bannan appeals the judgment of conviction
entered after a jury found him guilty of four felonies. We affirm.
I. Background
¶2 On October 16, 2019, A.M., an acupuncturist, arrived at her
office. As she opened her office door, Bannan, who was sitting in
the corner of her office, shot her in the arm. Bannan was a co-
owner of the building where A.M. worked. Police arrived and
arrested Bannan without incident. A.M. told police that after
Bannan shot her, he said to her, “I’m sorry, the Russian mafia is
after me.”
¶3 Bannan was charged with two counts of attempted first degree
murder, two counts of first degree assault, possession of a weapon
on school grounds,1 and four crime of violence sentence
enhancement counts. Bannan pleaded not guilty by reason of
insanity (NGRI). His case proceeded to a jury trial on August 30,
2021.
1 This charge appears to be based on an allegation that Bannan
possessed a firearm on the University of Colorado campus, which is near A.M.’s office. This charge, however, was voluntarily dismissed by the People prior to trial, so there is limited information about it in the record.
1 ¶4 At trial, Bannan’s defense was that he was unable to form the
requisite mental state for the charges under both an insanity and
involuntary intoxication theory. Bannan played defensive tackle for
several teams in the National Football League (NFL), and with
respect to NGRI, he claimed that multiple concussions that he
sustained during his football career negatively affected his brain
and prevented him from forming the requisite mental state. As for
involuntary intoxication, Bannan argued that he was overprescribed
Adderall, which also negatively affected his brain. The People
argued that Bannan was able to form the requisite mental state at
the time of the offense. Both sides presented multiple experts and
lay witnesses related to these issues.
¶5 The jury convicted Bannan of attempted first degree murder
(extreme indifference); first degree assault (deadly weapon); first
degree assault (extreme indifference); and the lesser included
offense of attempted second degree murder. After merging some of
the counts, the trial court sentenced Bannan to two concurrent
sentences of sixteen years in the custody of the Department of
Corrections.
2 II. Analysis
¶6 Bannan contends that the trial court erred by (1) limiting the
scope of his expert witnesses’ testimony; (2) limiting the scope of his
lay witnesses’ testimony; (3) limiting his cross-examination of the
prosecution’s expert witnesses; (4) allowing the prosecution to elicit
irrelevant testimony on cross-examination from his expert witness;
and (5) denying his request to call an expert witness in surrebuttal.
Bannan also contends that cumulative error warrants reversal. We
address, and reject, each contention in turn below.
A. Standard of Review
¶7 We review a trial court’s evidentiary decisions for an abuse of
discretion. People v. Murphy, 2021 CO 22, ¶ 16. A trial court
abuses its discretion when its decision was “manifestly arbitrary,
unreasonable, or unfair, or based on a misunderstanding or
misapplication of the law.” People v. Heredia-Cobos, 2017 COA 130,
¶ 6.
B. Scope of Expert Testimony
¶8 First, Bannan argues that the trial court erred by restricting
his experts’ testimony to the contents of their reports. The People
respond that the law requires such a limitation, otherwise criminal
3 defendants would be allowed to ambush the People with unexpected
arguments at trial. We conclude that, even if the court abused its
discretion by imposing this limitation, it didn’t reversibly err.
1. Additional Facts
¶9 At his arraignment, Bannan entered an NGRI plea. He
asserted that he suffered from chronic traumatic encephalopathy
(CTE)2 or other brain trauma that constituted a mental disease or
defect. As required by statute, the trial court ordered him to
undergo a sanity evaluation, which he did.
¶ 10 As part of his pretrial disclosures and as required by section
16-8-103.6(2)(a), C.R.S. 2025, Bannan disclosed to the People the
names and addresses of twelve treatment providers. Soon after,
Bannan supplemented this disclosure with two more names and
addresses of treatment providers. The trial court then ordered that
Bannan supplement this information with the providers’ telephone
numbers, the approximate dates of treatment, a general description
of the service each provided, and any diagnosis. Then, pursuant to
2 CTE is a brain disease linked to repeated trauma to the head. See Mayo Clinic, Chronic traumatic encephalopathy, https://perma.cc/SQT8-4RFN.
4 Crim. P. 16, Bannan disclosed seven expert witnesses. From our
review of the record, there isn’t any indication that Bannan failed to
comply with his statutory obligation to provide the People with
reports from these seven expert witnesses.
¶ 11 The People then filed a motion in limine to exclude any
evidence relating to CTE on the grounds that no treatment provider
had diagnosed Bannan as having such disease or disorder. The
trial court addressed this motion at a pretrial hearing. At the
hearing, the parties discussed whether Bannan would be seeking to
introduce evidence related to CTE. The parties clarified that doctors
can’t diagnose anyone with CTE until an autopsy is performed after
the patient’s death. But defense counsel explained that their
experts would opine that, based on Bannan’s behavior, conduct,
and head trauma history, they expect that after Bannan’s death he
would be diagnosed as having suffered from CTE during his
lifetime.
¶ 12 The People objected, arguing that this testimony wouldn’t be
relevant because it didn’t include a nexus between Bannan’s brain
trauma, including CTE, and his ability to form the requisite mental
state for the charged conduct. Defense counsel responded that this
5 connection wasn’t “something [the experts] would be able to opine
to because that [was] a question for the jury based on the evidence
presented.” But ultimately, defense counsel represented that they
believed that the expert testimony, when taken as a whole, would
show that CTE prevented Bannan from forming the requisite mental
state for the charged conduct.
¶ 13 The trial court allowed the defense to file a written response to
the People’s motion in limine and didn’t address the issue again
until the morning of the first day of trial. That morning, the trial
court explained that “[t]o the extent that the [c]ourt finds there
is . . . an expert whose expertise permits that witness to render an
expert opinion that [Bannan] presented consistent with other
individuals who have later been diagnosed with CTE, the [c]ourt
may be in a position of permitting that testimony.” Defense counsel
then clarified that the experts could testify that “to a reasonable
degree of medical probability” that Bannan suffers from CTE. The
trial court asked whether a report contained such an opinion and
ruled that if there wasn’t a report that did, then any testimony to
that regard wouldn’t be allowed.
6 ¶ 14 The trial court revisited this matter and ruled on what each
expert could testify to at trial. It repeated its earlier ruling that the
experts would be limited to testifying to matters only in their
reports. But it clarified that it would allow Dr. Marc Treihaft, one of
the defense experts, to testify about his impression that Bannan’s
symptoms may be a result of multiple concussions and CTE.
Defense counsel then reiterated their position that the connection
between the required mens rea and CTE, which the People still
asserted was lacking, was a question for the jury.
¶ 15 Later in the trial, Bannan called two of these experts —
Dr. John Hughes and Dr. Gregory Hipskind. The People objected to
parts of Dr. Hughes’s testimony on the basis that it was beyond the
scope of his report, and the trial court sustained those objections.
As Bannan argues on appeal, this testimony included the following:
• Defense counsel asked, “And what happens to the brain
internally when somebody has one of these external
concussive —” Dr. Hughes answered, “According to the
famous neurologist Robert Cantu, the brain goes into a —”
The prosecutor interrupted him, objecting that the
7 testimony was “beyond the scope of the opinion that was
discovered in this particular case.”
• Dr. Hughes testified about his opinion that Bannan suffered
from a traumatic brain injury. During that testimony, he
began speaking about Bannan’s computed tomography
angiogram that showed microvascular defects. The
prosecutor objected, explaining that “[n]o such document
has been provided in discovery” and “[n]or is it cited in . . .
the expert’s report.”
• Defense counsel asked, “And how long can symptoms from
one concussion affect somebody?” Dr. Hughes responded,
“A lifetime.” The prosecutor objected that this was “beyond
the scope of the report provided by this expert.” The trial
court sustained the objection and asked the jurors to
disregard the answer.
• Defense counsel asked, “Dr. Hughes, in [Bannan’s] case, the
traumatic brain injury, was it caused from one
concussion?” The prosecutor objected that this was
“beyond the scope of the material provided by this expert.”
8 • Defense counsel asked, “People with executive function
limitations, would you expect to see them running late
because of the decision-making aspect?” Dr. Hughes
responded, “[y]es.” The prosecutor objected that this was
“beyond the scope of this expert’s opinion.” The trial court
sustained the objection and asked the jury to disregard the
response.
• Defense counsel asked if Dr. Hughes’s opinion would
change if Bannan had been taking Adderall. Dr. Hughes
responded that “[i]f [Bannan] had been taking excessive
amounts of Adderall, that could have potentially pushed
him over the edge. I have had patients with traumatic brain
injury have seizures due to —” The prosecutor interrupted,
objecting that this was “well beyond the scope of this
witness’s provided report.”
¶ 16 Finally, during the testimony of another defense expert,
Dr. Karen Fukutaki, the trial court sustained an objection that her
testimony regarding when Bannan had brain surgery to place a
shunt in his brain was beyond the scope of the records she
reviewed.
9 2. Analysis
¶ 17 We address whether the trial court reversibly erred when it
limited defense experts to testifying about matters contained in
their reports. We conclude that it didn’t.
a. Standard of Reversal
¶ 18 We first discuss the proper standard of reversal. Bannan
contends that we should review his contentions for constitutional
error because the court’s rulings deprived him of a meaningful
opportunity to present a complete defense. People v. Cline, 2022
COA 135, ¶ 70. But such a deprivation only occurs “where the
defendant was denied virtually his only means of effectively testing
significant prosecution evidence.” People v. Conyac, 2014 COA 8M,
¶ 93. That isn’t the case here. The trial court’s ruling that the
defense experts could testify to only what was in their reports didn’t
virtually deny him of his only means of responding to the People’s
case. In fact, the experts were still able to testify to a wide variety of
opinions. See Cline, ¶ 79 (explaining that the defendant “had ample
opportunity to present evidence” through cross-examination of the
prosecution’s witnesses and direct examination of his witnesses).
10 ¶ 19 Also, Bannan presented evidence during trial to support his
theory of defense. His defense included testimony from two experts
who testified that Bannan suffered from a traumatic brain injury
and to the effects of such an injury, as well as that he was
prescribed about one hundred and fifty percent of the maximum
recommended dose of Adderall.
¶ 20 The defense also called witnesses to testify about Bannan’s
history of concussions. One of his ex-teammates testified that he
witnessed Bannan sustain many head injuries while playing
football. And an expert opined that Bannan suffered from
“hundreds to thousands of concussions” in his career. Upon our
review of the record, Bannan was permitted to present evidence
about his mental state, including the effect of multiple concussive
events and a traumatic brain injury. Therefore, Bannan was still
able to present a defense and rebut the People’s evidence. See
People v. Lanari, 926 P.2d 116, 122 (Colo. App. 1996) (concluding
that a defendant wasn’t denied his constitutional right to present a
defense when defense witnesses testified to his state of mind before
and after the offense).
11 ¶ 21 In sum, because the trial court’s ruling still permitted the
experts to testify to what was in their reports, including testimony
about his mental state, we can’t say that it barred Bannan from
subjecting the prosecution’s case to “meaningful adversarial
testing.” Krutsinger v. People, 219 P.3d 1054, 1061 (Colo. 2009).
Therefore, the non-constitutional harmless error applies. Under
that standard, “reversal is required only if the error affects the
substantial rights of the parties.” Hagos v. People, 2012 CO 63,
¶ 12. Meaning, “we reverse if the error ‘substantially influenced the
verdict or affected the fairness of the trial proceedings.’” Id.
(citation omitted).
b. Any Error was Harmless
¶ 22 Now, applying that standard, and assuming that the trial
court abused its discretion in ordering Bannan’s expert witnesses to
testify to only matters in their reports, we conclude that any error
was harmless, as defense counsel didn’t make an adequate offer of
proof — either to the trial court or us on appeal — as to what the
experts would have testified to that was outside of their reports had
they been permitted to do so and why that proffered testimony
would have been materially helpful to Bannan’s theory of defense.
12 See People v. Drake, 748 P.2d 1237, 1245-46 (Colo. 1988)
(concluding that any error by the trial court in sustaining the
prosecution’s objections to certain portions of a defense expert’s
testimony wasn’t sufficiently prejudicial to warrant reversal because
“the defendant did not make an offer of proof to the trial court to
establish for the record precisely what [the expert] would have said,
had he been permitted to testify”); People v. Hise, 738 P.2d 13, 16
(Colo. App. 1986) (explaining that failure to give a sufficient offer of
proof left the reviewing court unable to determine in what way the
exclusion of evidence was prejudicial and so any error was
harmless). We reach this conclusion because we can’t discern from
the record that the defense was seeking to offer any evidence
establishing a link between CTE and the ability to form criminal
intent.
¶ 23 Defense counsel did represent to the trial court that some of
their experts, if permitted to, could testify to a reasonable degree of
medical probability that Bannan suffers from CTE. But this offer of
proof is missing any link to how suffering from CTE likely affected
Bannan’s ability to formulate the requisite mental state for the
crimes charged. Defense counsel only vaguely mentioned that,
13 when considered in the aggregate, the sum of the defense experts’
testimony might show this connection. But when the trial court
directly asked defense counsel whether their witnesses could testify
that Bannan’s likely CTE prevented him from formulating the
requisite mental state, defense counsel said no and explained that
was an ultimate conclusion that was left for the jury.
Notwithstanding this, the record doesn’t reveal the details of what
each expert would have said beyond what was already in their
reports. And without this link, we can’t conclude that Bannan was
prejudiced by any error in excluding testimony about whether he
likely suffers from CTE.
¶ 24 The trial court recognized that testimony about the nexus
between CTE and Bannan’s ability to form the requisite mental
state was likely admissible. The court said that to the extent it
found that there was an “expert whose expertise permits that
witness to render an expert opinion that [Bannan] presented
consistent with other individuals who have later been diagnosed
with CTE, the [c]ourt may be in a position of permitting that
testimony.” Therefore, it’s unclear if the trial court even would have
sustained an objection by the prosecutor that such testimony was
14 outside the expert’s report had the defense sought to have their
experts testify to this.
¶ 25 Also, Bannan’s experts were still permitted to testify to the
opinions contained in their report, which included Dr. Hughes’s
opinion that Bannan suffered from a traumatic brain injury,
Dr. Hipskind’s opinion that Bannan had a “classic traumatic brain
injury pattern”, and Dr. Fukutaki’s opinion that Bannan was
prescribed about one hundred and fifty percent of the maximum
recommended dose of Adderall. All this testimony supported his
theory of defense. See Drake, 748 P.2d at 1246 (recognizing that, in
analyzing whether a defendant was sufficiently prejudiced by
excluded portions of his expert’s testimony, that the jury was still
informed of the expert’s opinion).
¶ 26 Simply put, without a sufficient offer of proof, we can’t
conclude that the excluded testimony about whether Bannan
suffered from CTE prejudiced him. See Lanari v. People, 827 P.2d
495, 503 (Colo. 1992) (“An offer of proof also serves the important
purpose of establishing a basis in the record for appellate review of
the trial court’s ultimate ruling.”). And when we look at the
testimony Bannan asserts was improperly excluded on appeal, none
15 of it addresses this missing nexus. Similarly, since we don’t have
an offer of proof as to what the answers would have been to the
seven questions to which objections were sustained, we can’t say
the court’s ruling on these objections prejudiced Bannan. See
Rhodig v. Cummings, 418 P.2d 521, 502 (Colo. 1966) (concluding
there was no reversible error when the trial court precluded defense
experts from testifying to certain matters because “the defendant
failed to make an offer of proof to show to the trial court or this
[c]ourt what the testimony of the doctors” would have been); cf.
People v. Sandoval, 805 P. 2d 1126, 1128 (Colo. App. 1990)
(concluding that the trial court erred in excluding evidence and
such exclusion wasn’t harmless because “defense counsel made an
offer of proof” that “defendant’s abnormal behavior [was] caused by
his underlying, psychological condition” (emphasis added)).
¶ 27 Accordingly, we conclude that any error by the trial court in
limiting the defense experts’ testimony to their reports was
harmless.
C. Scope of Lay Witness Testimony
¶ 28 Second, Bannan contends that the trial court erred when it
ruled that one of his lay witnesses, Mitchell Unrein, couldn’t testify
16 that Bannan’s “brain was sick” because such testimony was an
expert opinion. He also contends that the trial court erred when it
sustained the People’s objection to testimony from Unrein and Beau
Williams (a lay witness called by the People) about their personal
experiences with concussions on relevance grounds. We disagree
with both contentions.
¶ 29 Both Unrein and Williams are former NFL players. On the first
day of trial, defense counsel explained to the trial court that he
intended to call lay witnesses to opine that Bannan’s “brain was
sick” and that Bannan “didn’t seem normal” to them. The trial
court explained that it would sustain an objection to the former
statement because it was “in the way of a diagnosis.”
¶ 30 Then during trial, the trial court sustained the People’s
objections to the lay witnesses testifying about their own personal
experience with brain trauma due to playing football. Unrein
testified that “[b]ut, for me, I’m like — I was going through the same
thing. So, like, when he was going through all that, I mean, I —
your mind starts playing tricks on you. It’s — you can’t control
what your thoughts are.” The People objected that this was
17 improper expert testimony. After a discussion at the bench, the
trial court ruled that if Unrein was referring to his own mind, such
testimony was irrelevant. The trial court also sustained the
People’s relevance objection as to Williams’s testimony about his
own personal experience of being knocked out while playing
football.
2. Applicable Law
¶ 31 CRE 701 provides that
If the witness is not testifying as an expert, the witness’ testimony in the form of opinions or inferences is limited to those opinions or inferences which are (a) rationally based on the perception of the witness, (b) helpful to a clear understanding of the witness’ testimony or the determination of a fact in issue, and (c) not based on scientific, technical, or other specialized knowledge within the scope of Rule 702.
¶ 32 And section 16-8-109, C.R.S. 2025, provides that
In any trial or hearing in which the defendant’s mental condition is an issue, a witness not specially trained in psychiatry or psychology may testify as to the witness’s observation of the defendant’s actions and conduct, and as to conversations that the witness has had with the defendant bearing upon the defendant’s mental condition, and the witness must be permitted to give opinions or conclusions concerning the defendant’s mental condition.
18 ¶ 33 In interpreting this statute, the Colorado Supreme Court has
explained that it doesn’t “allow[] a lay witness to opine as to a
defendant’s specific diagnosis.” Dunlap v. People, 173 P.3d 1054,
1098 (Colo. 2007).
¶ 34 Further, evidence must be relevant to be admissible. CRE
402. Relevant evidence is “evidence having any tendency to make
the existence of any fact that is of consequence to the determination
of the action more probable or less probable than it would be
without the evidence.” CRE 401.
3. Analysis
¶ 35 First, the trial court didn’t abuse its discretion by precluding
Unrein from testifying that Bannan’s “brain was sick” pursuant to
CRE 702, as such testimony can be reasonably characterized as
offering a diagnosis. See Dunlap, 173 P.3d at 1098. In reaching its
conclusion that the precluded testimony was inadmissible, the
court distinguished it from Unrein’s permissible lay opinion that
Bannan “didn’t seem normal” to him. We can’t say that the trial
court abused its discretion in drawing the line that it did.
¶ 36 Second, Bannan argues that the trial court erred in sustaining
the People’s objections on relevance grounds to witnesses testifying
19 to their own personal experiences with brain trauma. He contends
that the testimony was proper under CRE 701 and section 16-8-
109. Specifically, he argues that the statute allows lay opinions
based on personal experience, and that the excluded testimony was
proper because it helped lay the foundation for witnesses’ lay
opinions as to Bannan’s mental state. We aren’t persuaded.
¶ 37 While section 16-8-109 allows a lay witness to testify as to
their personal experience with the defendant’s mental condition, it
doesn’t permit the witness to testify regarding their own personal
experience generally. See § 16-8-109 (explaining that a lay witness
“may testify as to the witness’s observation of the defendant’s
actions and conduct” (emphasis added)).
¶ 38 Moreover, the two foundational requirements “which must be
met before a lay witness can express his opinion as to the sanity of
another” are “(1) it must be shown that the lay witness had an
adequate means of becoming acquainted with the person whose
sanity is in issue, and (2) the contacts must be proximate in time to
the alleged offense.” People v. Medina, 521 P.2d 1257, 1259 (Colo.
1974). A witness’s personal experience with head trauma doesn’t
help establish either of these foundational requirements. And the
20 People don’t dispute that Bannan laid the proper foundation for
both Unrein and Williams to testify about Bannan’s mental status.
But we reject Bannan’s contention that the witnesses’ testimony
about their own experience with head trauma was proper
foundational testimony. Bannan also hasn’t explained why this
testimony tended to make a fact of consequence more or less
probable. CRE 401. Accordingly, we conclude that the trial court
didn’t abuse its discretion by limiting the scope of lay witness
testimony as it did at trial.
D. Scope of Cross-Examination of Prosecution Witnesses
¶ 39 Next, Bannan argues that the trial court erred by sustaining
the People’s beyond the scope and relevancy objections during
Bannan’s cross-examination of three prosecution witnesses. We
discern no abuse of discretion.
1. Beyond the Scope of Direct Examination
¶ 40 CRE 611(b) provides that cross-examination “should be limited
to the subject matter of the direct examination and matters
affecting the credibility of the witness” but that “[t]he court may, in
the exercise of [its] discretion, permit inquiry into additional matters
as if on direct examination.” The beyond the scope objections that
21 Bannon challenges on appeal came during the testimony of
Dr. John Geraghty, who was Bannan’s team doctor when he played
for the Broncos and continued treating Bannan after Bannan
stopped playing football.
¶ 41 Dr. Geraghty’s testimony on direct examination focused on his
treatment of Bannan for attention deficit disorder (ADD), including
Bannan’s ADD symptoms, Dr. Geraghty prescribing Bannan
Adderall, Bannan’s request to refill that prescription, his
conversations with Bannan about the risks and dangers of Adderall,
the amount of Adderall he prescribed for Bannan, and his
subsequent decision to switch Bannan’s prescription from Adderall
to Provigil. The People also asked Dr. Geraghty two questions about
concussions — one, if he recalled treating Bannan for a concussion
in March 2019 (he said he didn’t); and two, if he recalled whether
Bannan had any concussions after his NFL career (he wasn’t aware
of any). In sum, Dr. Geraghty’s direct testimony centered on him
prescribing Bannan Adderall.
¶ 42 As relevant here, the People objected five times during defense
counsel’s cross-examination of Dr. Geraghty. The trial court
sustained all five of the objections, ruling that the questions were
22 beyond the scope of the direct examination. Those questions were
as follows:
(1) “So you’re aware that [Bannan] had brain surgery in
October 2020?”
(2) “And, Dr. Geraghty, have you reviewed the records from
Mr. Bannan’s other physicians?”
(3) “Have you ever reviewed a SPECT scan done of Mr.
Bannan?”
(4) “Have you reviewed a report in this case drafted — or
written by Dr. Fukutaki?”
(5) “Were you aware of Mr. Bannan having brain trauma?”
¶ 43 Also during Dr. Geraghty’s testimony, defense counsel asked
him a sixth question that is pertinent to the appeal,
(6) “And when you met with Mr. Bannan, the first time you
met with him for a physical after the . . . October 16th,
2019, shooting incident, did you discuss any other
concerns that he had, medically speaking, in ongoing
treatment?”
¶ 44 The People objected that this question was beyond the scope of
direct examination, and the trial court told defense counsel to
23 narrow the question “as to the discontinuation of the Adderall.”
Defense counsel then asked, “Doctor, this is when you discontinued
Mr. Bannan’s Adderall, right?”
¶ 45 Bannan argues that defense counsel asked all six of these
questions to impeach Dr. Geraghty’s credibility, so the court abused
its discretion in sustaining the objection as beyond the scope of
direct examination. We aren’t persuaded that the court abused its
discretion.
¶ 46 Again, Dr. Geraghty’s testimony on direct centered on
prescribing Bannan Adderall, which started around 2013, and the
symptoms Bannan was experiencing related to ADD. At no point
did the People ask Dr. Geraghty about reports or recommendations
from other health care providers. Therefore, defense counsel’s
questions on cross-examination weren’t “germane to the direct
examination” and didn’t “qualify[] or destroy[] it, or tend[] to
elucidate, modify, explain, contradict, or rebut testimony.” People
v. Sallis, 857 P.2d 572, 574 (Colo. App. 1993). Dr. Geraghty only
testified on direct as to his opinions and treatment of Bannan for
ADD.
24 ¶ 47 And we aren’t persuaded that defense counsel’s questions
relating to other doctors went to Dr. Geraghty’s credibility and thus
should have been allowed. Bannan has failed to explain why
Dr. Geraghty’s review, or failure to review, other doctors’ reports or
recommendations would impugn his credibility. Dr. Geraghty
prescribed Bannan Adderall, and we fail to see how his alleged
failure to review all of Bannan’s other medical records would have
undermined his testimony about Bannan’s Adderall prescription
and symptoms. And even if such questions implicated
Dr. Geraghty’s credibility, the trial court could have reasonably
found that the danger of confusing the jury — because it implicated
issues not related to Dr. Geraghty — outweighed any probative
value to his credibility. Therefore, the trial court didn’t abuse its
discretion in sustaining the People’s objection to defense counsel’s
questions to Dr. Geraghty about Bannan’s other doctors’ reports
and recommendations. See People v. Marin, 686 P.2d 1351, 1353
(Colo. App. 1983) (“The right of cross-examination extends only to
areas encompassed in direct examination, and anything outside of
direct examination is completely discretionary with the court.”).
25 ¶ 48 The trial court also didn’t abuse its discretion by sustaining
the People’s objections to defense counsel’s questions about
Bannan’s brain trauma for being beyond the scope of direct
examination. Again, the People didn’t ask Dr. Geraghty about these
topics on direct examination, so it was within the trial court’s
discretion to not allow defense counsel to ask Dr. Geraghty about
them on cross-examination.
¶ 49 In fact, Dr. Geraghty testified on cross-examination that
additional knowledge about Bannan’s history of brain trauma
wouldn’t have impacted his decision to prescribe Adderall for his
ADD. The trial court allowed the following exchange between
defense counsel and Dr. Geraghty on cross-examination right before
the fifth question:
[DEFENSE COUNSEL]: And you would be . . . concerned about somebody taking Adderall with concussions; isn’t that right?
[DR. GERAGHTY]: Actually, through other doctors that I have interacted with who have dealt with brain traumas, it’s not an unusual medication to use.
26 ¶ 50 This testimony established that any trauma to Bannan’s brain
wouldn’t have been a concern for Dr. Geraghty when he was
deciding whether to prescribe Adderall to Bannan.
¶ 51 And the People’s two questions on direct examination about
concussions don’t change this analysis. These specific questions
about Bannan’s concussion history didn’t open the door for defense
counsel to ask Dr. Geraghty more generally about brain trauma and
Bannan’s other doctors’ opinions on cross-examination because
they focused on Dr. Geraghty’s own knowledge of Bannan’s
concussion history, of which he had none. Accordingly, we discern
no error in any of the trial court’s rulings regarding these six
questions.
2. Relevance
¶ 52 Bannan challenges the court’s ruling sustaining three
relevance objections raised by the People. We address each
question, in turn, below.
¶ 53 The first question was to Dr. James Kelly, the People’s expert
witness in neurology and traumatic brain injury. Right before the
question challenged on appeal, Dr. Kelly had testified that Bannan
had some limitation in moving his neck. Defense counsel then
27 asked, “And what was the limitation? He couldn’t turn his head all
the way around?” The trial court sustained the People’s objection to
this question on relevance grounds.
¶ 54 Bannan argues that the details of his neck injury were
relevant because they would have supported an inference that his
brain injury was more severe than one unaccompanied by a neck
injury. But Bannan doesn’t explain why whether he had limited
ability to turn his neck to the side as opposed to a limited ability to
bend it up and down makes it more or less likely that he suffered a
severe brain injury. See People v. Moore, 2021 CO 26, ¶ 33
(“[E]vidence that is ‘relevant to the issue of insanity’ is evidence that
tends to prove or disprove the issue of insanity — that is, evidence
that is probative of what is defined as insanity.” (quoting § 16-8-
107(3)(a), C.R.S. 2025)). So, we discern no abuse of discretion in
the trial court’s relevancy ruling.
¶ 55 The second question was to Dr. Charles Harrison, who
conducted Bannan’s first sanity evaluation. The People asked him,
“Did [Bannan] express to you any additional treatment that he had
other than [lumbar punctures, barometric treatments, oxygen
chambers, and stem cell treatments] or had planned to have?”
28 ¶ 56 Bannan argues that understanding the treatment he had or
planned to undergo after the shooting was relevant to his claim that
he had a mental condition that prevented him from forming the
required mens rea. But, again, Bannan doesn’t explain why other
treatments, especially any planned for the future, would have
impacted his ability to form the requisite mens rea at the time of the
offense. Without that connection, we discern no abuse of discretion
in the trial court’s refusal to permit defense counsel to ask this
question.
¶ 57 The third question was to Dr. Geraghty. After previously
prescribing Adderall to treat Bannan’s ADD, Dr. Geraghty changed
the prescription to Provigil. After confirming with Dr. Geraghty that
a patient could get “no refills” on a single Adderall prescription,
defense counsel asked, “[I]n 2019, Provigil had . . . only three refills
[that] could be allowed . . .?”
¶ 58 Bannan argues that because more refills are allowed for
Provigil than for Adderall, that means Provigil isn’t as highly
regulated as Adderall, indicating that there are greater risks
associated with taking Adderall. Therefore, he argues, this question
was relevant to his defense that he was involuntary intoxicated due
29 to his high Adderall prescription. Bannan asks us to infer that
because Adderall is more regulated than Provigil, there are more
risks to taking Adderall. But he hasn’t provided evidence of this
inference, and without that, we discern no abuse of discretion by
the trial court in excluding this testimony on relevancy grounds.
¶ 59 Accordingly, the trial court didn’t abuse its discretion in
sustaining relevance objections to these three questions.
E. Scope of Cross-Examination of Defense Witness
¶ 60 Bannan next argues that the trial court abused its discretion
by allowing the People to elicit irrelevant testimony from
Dr. Fukutaki, a defense expert witness. Again, we disagree.
¶ 61 After pleading NGRI, Bannan underwent his first sanity
evaluation per the trial court’s order. The evaluating doctor opined
that Bannan was sane at the time of the offense. After that
evaluation was completed, Bannan requested that the trial court
order a second sanity evaluation to be completed by a different
evaluator, Dr. Fukutaki, pursuant to section 16-8-108(1)(a), C.R.S.
2025. The trial court granted his request, explaining that an
independent order for an evaluation would issue and that the
30 interview must be video and audio recorded, as required by statute.
See § 16-8-108(1)(a). But due to an administrative error by the
court, the order issued was for a second competency evaluation, not
for a sanity evaluation. Competency evaluations aren’t required to
be recorded. See § 16-8.5-102 to -103, C.R.S. 2025.
¶ 62 A couple of weeks later, Bannan filed a motion to clarify this
order. In response, the trial court set aside the mistaken
competency order and issued a new order for a second sanity
evaluation to be completed by Dr. Fukutaki. But before the
corrected order issued, Dr. Fukutaki completed her evaluation of
Bannan. Thus, at the time of her evaluation, the only order she
had from the court was for a competency evaluation. Dr. Fukutaki
didn’t audio or video record the interview.
¶ 63 Bannan called Dr. Fukutaki to testify as an expert at trial.
Before her testimony, Bannan asked that the trial court exclude as
irrelevant any testimony or questioning regarding her evaluation
not being recorded pursuant to section 16-8-108(1)(a). The People
explained that they intended to ask questions on the matter
because Dr. Fukutaki’s decision to not record the evaluation went
“directly to her bias and motive, and any assertion that
31 Dr. Fukutaki was unaware that a sanity evaluation had been
ordered in this case lacks credence based on the fact that she took
the unusual step, in a competency evaluation, to address the issue
of insanity.” Indeed, after opining that Bannan was competent to
proceed, Dr. Fukutaki wrote that Bannan “denied guilt for the
charges he faces. He reported his gun accidentally discharged,
leading to the injury [A.M.] suffered. Therefore, offering an opinion
regarding sanity appears unethical.” The trial court ruled that it
might permit the People’s questions if it determined that they bore
on Dr. Fukutaki’s credibility or bias.
¶ 64 As relevant here, the trial court overruled Bannan’s objections
to the People’s cross-examination of Dr. Fukutaki on three
occasions. The questions by the People were as follows:
• “Doctor, are you aware that the Court in this case issued an
order on November 20th, 2020, authorizing you to conduct
a sanity evaluation in this case at the request of [defense
counsel]?”
• “You would agree, Doctor, that the statute requires sanity
evaluations be recorded?”
32 • “And you would agree, Doctor, that when we’re talking
about a competency evaluation, as it’s authorized by
statute, that a competency evaluation as authorized by
statute does not address issues of sanity?”
¶ 65 “[T]he partiality of a witness is always relevant.” Margerum v.
People, 2019 CO 100, ¶ 10. Indeed, “when a witness testifies
against a party, the party has a right to impeach that witness’s
credibility.” Id. at ¶ 11. “Any witness’s credibility can be attacked
by unearthing any potential source of impartiality, such as bias or
an ulterior motive.” Id. at ¶ 10. But a trial court must exercise its
discretion to preclude inquiries that “have little effect on the
witness’ credibility but would substantially impugn [their] moral
character.” People v. Taylor, 545 P.2d 703, 705 (Colo. 1976).
¶ 66 Bannan argues that the trial court erred in overruling his
objections to three of the People’s questions of Dr. Fukutaki on
cross-examination. Specifically, he argues that the testimony was
irrelevant, not probative of her credibility, and misleadingly
impugned her character. We disagree with each contention.
33 ¶ 67 The trial court didn’t abuse its discretion in concluding that
the three questions identified above were relevant to Dr. Fukutaki’s
credibility as a defense expert witness. The timing of events is
critical to reaching this conclusion. Although the court issued the
corrected order for a sanity evaluation after Dr. Fukutaki completed
the competency evaluation, it did so before she completed her
report. And it’s certainly a reasonable area of inquiry as to why
Dr. Fukutaki opted not to perform a statutorily compliant sanity
evaluation after receiving the corrected order. In other words, it
was the People’s proposition that Dr. Fukutaki could have redone
the evaluation as a sanity evaluation pursuant to the new order.
Therefore, we can’t conclude that it was an abuse of discretion for
the trial court to permit the People to inquire into Dr. Fukutaki’s
reasoning for not recording the evaluation or even re-doing the
evaluation pursuant to the new order. Indeed, Bannan had filed
the motion to clarify (explaining that the court’s order should have
been for a sanity evaluation) three days before Dr. Fukutaki
completed her evaluation. And Dr. Fukutaki didn’t file her written
report with the court until almost four months after the court
issued the corrected order. Therefore, the trial court didn’t abuse
34 its discretion in overruling Bannan’s objections because the
circumstances suggested that Dr. Fukutaki could have known that
the competency order was a mistake and that she should have been
conducting a sanity evaluation. See Ross v. Colo. Nat’l Bank of
Denv., 463 P.2d 882, 887 (Colo. 1969) (“[O]nce a witness testifies as
an expert, he subjects himself to the most rigid kind of cross-
examination . . . .”); see also People v. Houser, 2013 COA 11, ¶ 58
(“[C]ourts have wide latitude to reasonably limit cross-
examination . . . .”). So, the People could inquire into these
circumstances.
¶ 68 Furthermore, these questions didn’t cross the line from
impeaching her credibility to impugning her character. Again, these
questions related to court orders and an evaluation for the pending
case. Cf. People v. Cole, 654 P.2d 830, 833-34 (Colo. 1982)
(explaining that questions about “unrelated arrests and citizen
complaints of the use of excessive force” of a police officer was a
“direct attack upon the general character of the witness”).
Dr. Fukutaki could have had a reasonable explanation for why she
didn’t record the evaluation or why she didn’t conduct a new sanity
35 evaluation. Nothing about this line of inquiry impugned her
character.
¶ 69 Accordingly, we discern no error by the trial court in
overruling Bannan’s relevance objections to the People’s cross-
examination of Dr. Fukutaki.
F. Surrebuttal Expert Witness
¶ 70 Fifth, Bannan argues that the trial court erred by denying his
request to call an expert witness, Dr. Kevin Lillehei, in surrebuttal.
We disagree.
¶ 71 Both Bannan and the People endorsed Dr. Lillehei as an
expert witness but neither side ended up calling him to testify in
their case-in-chief. The People presented twelve witnesses in their
rebuttal case, none of whom were Dr. Lillehei. After the People’s
presentation of their rebuttal case, Bannan requested that he be
allowed to call Dr. Lillehei as a surrebuttal expert witness.
¶ 72 After hearing argument from both sides on this request, the
trial court explained that it “agree[d] [with the People] that it is
appropriate to consider surrebuttal only in instances where there is
presentation in the rebuttal case of evidence that then permits a
36 surrebuttal case, which in the [c]ourt’s opinion in this instance,
there was not.” The trial court then denied Bannan’s request to call
Dr. Lillehei in surrebuttal.
¶ 73 “A decision whether to allow surrebuttal generally lies within
the discretion of the trial court.” People v. Brockman, 699 P.2d
1339, 1342 (Colo. 1985). But “trial courts should permit
defendants to introduce evidence on surrebuttal that tends to meet
new matter presented by the prosecution on rebuttal.” People v.
Terry, 720 P.2d 125, 129 (Colo. 1986).
¶ 74 Bannan argues that in denying his request to call Dr. Lillehei
in surrebuttal, the trial court misapplied the law — and thus
abused its discretion — because the trial court misapprehended the
scope of its discretion. It did so, he argues, because the court
erroneously explained it could only allow surrebuttal if new matter
was introduced on rebuttal, but the law is that the court does have
discretion to allow surrebuttal even if new matter hadn’t been
presented on rebuttal. The People respond that the trial court
recognized it had discretion to allow surrebuttal even if rebuttal
37 didn’t introduce new matter and exercised that discretion to not
permit surrebuttal because there wasn’t a reason to do so based on
its assessment of the evidence.
¶ 75 To be clear, Bannan doesn’t contend on appeal that he sought
to call Dr. Lillehei in surrebuttal to respond to new information
presented by the People in their rebuttal case. Therefore, it was
within the trial court’s discretion to deny Bannan’s request for
Dr. Lillehei to testify in surrebuttal. People v. Martinez, 506 P.2d
744, 745 (Colo. 1973).
¶ 76 And we aren’t persuaded that the trial court improperly
exercised this broad discretion. To be sure, the trial court stated
that “it is appropriate to consider surrebuttal only in instances
where there is presentation in the rebuttal case of evidence that
then permits a surrebuttal case.” This, however, wasn’t a
misapplication of the law. The trial court didn’t say that it could
only permit surrebuttal if new matter had been presented on
rebuttal, as Bannan argues. Instead, the trial court explained when
it considered surrebuttal proper (i.e., “where there is presentation in
the rebuttal case of evidence that then permits a surrebuttal case”)
and then found that those circumstances weren’t present for
38 Bannan’s case. This wasn’t an abuse of discretion by failure to
exercise discretion because the court, contrary to Bannan’s
argument on appeal, seemed to have exercised its discretion in
denying Bannan’s request. Put differently, the trial court didn’t
abuse its discretion by not allowing Bannan to call a surrebuttal
witness when the law didn’t require the trial court to allow him to
call such a witness and it explained that it didn’t believe the
proposed surrebuttal was proper for Bannan’s case, thereby
exercising its discretion.
¶ 77 Accordingly, we conclude that the trial court didn’t abuse its
discretion in denying Bannan’s request to call Dr. Lillehei in
surrebuttal.
G. Cumulative Error
¶ 78 Finally, Bannan contends that the cumulative effect of the
errors asserted on appeal requires reversal. “For reversal to occur
based on cumulative error, a reviewing court must identify multiple
errors that collectively prejudice the substantial rights of the
defendant, even if any single error does not. Stated simply,
cumulative error involves cumulative prejudice.” Howard-Walker v.
People, 2019 CO 69, ¶ 25.
39 ¶ 79 We have assumed that the trial court erred regarding
Bannan’s first issue on appeal. But we concluded that any error
was harmless and didn’t prejudice him. We reached this
conclusion because Bannan didn’t explain what his experts’
testimony would have been had the trial court allowed the experts
to testify to matters outside their reports. Without this offer of
proof, again, we’re unable to articulate how this missing testimony
prejudiced Bannan. Therefore, because there is no articulation of
prejudice to Bannan from the only error we assume on appeal, the
cumulative error doctrine doesn’t provide an independent basis for
reversal. See People v. Thames, 2019 COA 124, ¶ 69 (“[A] single
error is insufficient to reverse under the cumulative error
standard.”).
III. Disposition
¶ 80 The judgment is affirmed.
JUDGE GROVE and JUDGE JOHNSON concur.