2026 CO 23 24SC244, Lopez, Gustavo v. People

OCR transcription for search; preserved printed pages are authoritative

The opinion summaries are not part of the Colorado Supreme
Court's opinion. They have been prepared solely for the reader's
convenience. As such, they may not be cited or relied upon. If
there is any discrepancy between the language in the summary
and the opinion, the language in the opinion controls.

ADVANCE SHEET HEADNOTE
April 13, 2026

2026 CO 23

No. 24SC244, Lopez v. People-Evidence-Opening the Door Doctrine-
Admissibility of Expert Witness Testimony- Expert Coaching Testimony-
CRE 608(a) -CRE 702-Golob v. People, 180 P.3d 1006 (Colo. 2008) -People v.
Snook, 745 P.2d 647 (Colo. 1987) - People v. Gaffney, 769 P.2d 1081 (Colo. 1989) -
People v. Fasy, 829 P.2d 1314 (Colo. 1992) - Venalonzo v. People, 2017 CO 9,
388 P.3d 868.

In this child sexual assault case, the district court admitted expert testimony
from a forensic interviewer who, in response to a juror's question, stated that she
observed no signs indicative of coaching during her interviews with the child
victims. The defendant appealed, arguing that the expert's testimony was
effectively an opinion on the child victims' truthfulness on a particular occasion,
which is inadmissible. A split division of the court of appeals agreed with the
defendant that the expert's response to the juror's question was inadmissible,
reasoning that an expert witness may not testify about the lack of indicia of
coaching during a child victim's interview because such testimony is analogous to
an improper opinion about another witness's truthfulness on a particular occasion.
But the division nevertheless upheld the trial court's ruling under the opening the

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door doctrine. It determined that the defense had opened the door to the
otherwise inadmissible testimony by persistently advancing the theory at trial that
the children's maternal grandmother wanted to keep custody of them and had
therefore coached them or otherwise influenced them to fabricate the allegations
or form false memories of abuse.

The supreme court affirms. Assuming, without deciding, that the testimony
at issue was inadmissible, the court holds that the defense opened the door to it by
repeatedly suggesting to the jury - through both the introduction of evidence and
the presentation of argument-that the children had been coached or otherwise
improperly influenced by their maternal grandmother because she wanted to
maintain custody of them. By consistently attacking the credibility of the children
with assertions that they had been coached or otherwise improperly influenced,
the defense opened the door to the expert's testimony that she perceived no
indication of coaching.

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# The Supreme Court of the State of Colorado 2 East 14th Avenue . Denver, Colorado 80203

2026 CO 23

Supreme Court Case No. 24SC244
Certiorari to the Colorado Court of Appeals
Court of Appeals Case No. 19CA2313

Petitioner:
Gustavo Lopez,

V.

Respondent:

The People of the State of Colorado.

Judgment Affirmed
en banc
April 13, 2026

Attorneys for Petitioner:

Megan A. Ring, Public Defender

Meghan M. Morris, Deputy Public Defender

Denver, Colorado

Attorneys for Respondent:

Philip J. Weiser, Attorney General

Frank R. Lawson, Senior Assistant Attorney General

Denver, Colorado

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JUSTICE SAMOUR delivered the Opinion of the Court, in which JUSTICE
HOOD, JUSTICE GABRIEL, and JUSTICE BERKENKOTTER joined.
CHIEF JUSTICE MÁRQUEZ, joined by JUSTICE BOATRIGHT and JUSTICE
BLANCO, dissented.

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JUSTICE SAMOUR delivered the Opinion of the Court.

11 "[O]ne who induces a trial court to let down the bars to a field of inquiry
that is not competent or relevant to the issues cannot complain if his adversary is
also allowed to avail himself of the opening." 1 Kenneth S. Broun et al., McCormick
on Evidence § 57, Westlaw (Robert P. Mosteller ed., 9th ed. database updated Feb.
2025) (quoting Warren Live Stock Co. v. Farr, 142 F. 116, 117 (8th Cir. 1905)). The
majority of courts seem to heed this general principle of "fighting fire with fire,"
though it is known by different monikers. See id .; see also Bearint ex rel. Bearint v.
Dorel Juv. Grp., Inc., 389 F.3d 1339, 1349 (11th Cir. 2004) ("This Circuit recognizes
the concept of 'curative admissibility' - also called 'opening the door' or 'fighting
fire with fire."). In Colorado, the principle travels under the banner of "opening
the door." See, e.g., People v. Melillo, 25 P.3d 769, 775 (Colo. 2001).

T2
Courts across the country beat to different drums in their application of the
door-opening principle. 1 Broun et. al, supra, § 57. In Hemphill v. New York, 595
U.S. 140, 152 (2022), for example, the Supreme Court observed that New York's
version of the principle requires state courts "to determine whether one party's
evidence and arguments, in the context of the full record, have created a
'misleading impression' that requires correction with additional material from the
other side." Colorado largely speaks the same language as New York when it
comes to the opening the door doctrine. See People v. Murphy, 919 P.2d 191, 195

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(Colo. 1996). We have explained that a party may open the door to otherwise
inadmissible evidence by selectively presenting "facts that, without being
elaborated or placed in context, create an incorrect or misleading impression."1
Golob v. People, 180 P.3d 1006, 1012 (Colo. 2008) (citing Murphy, 919 P.2d at 195).
The doctrine aims to prevent a party "from gaining and maintaining an unfair
advantage" at trial. Id .; see also People v. Miller, 890 P.2d 84, 98-99 (Colo. 1995)
(same).

13
In this sexual assault on a child case, the People presented the testimony of
Kim Grimm, who conducted the forensic interviews with the child victims, N.L.
and A.L. After Grimm described her interviews with N.L. and A.L. and offered
generalized expert opinions on conducting forensic interviews with children in
criminal cases-including the signs of coaching she is trained to look for - a juror
submitted a question for her. The juror inquired whether the child victims'

1 We are aware that in common parlance lawyers and judges often use "opening
the door" imprecisely, including to permit admissible evidence to refute or rebut an
argument or other evidence. See generally People v. Miller, 890 P.2d 84, 99 (Colo.
1995) (citing 21 Wright & Miller's Federal Practice & Procedure § 5039 (1977)), for the
proposition that trial courts and appellate courts alike often create confusion by
using terms like "opening the door," "fighting fire with fire," and "curative
admissibility" in situations requiring analysis pursuant to the rules of evidence).
In this opinion, when we refer to opening the door, we mean the doctrine that
allows a party to present otherwise inadmissible evidence because the opposing
party has selectively introduced information that leaves the factfinder with an
inaccurate or misleading impression.

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behaviors during Grimm's interviews were consistent with the behaviors of
children she'd observed in cases where she'd discerned that coaching had
occurred. Defense counsel objected, arguing that the question called for Grimm
to offer an expert opinion on the credibility of the children. But the trial court
overruled the objection and allowed the question. Grimm then testified that she
didn't "feel like [she] saw huge red flags with that or anything that indicated that."
Elaborating, she stated that each child was able to provide very specific
experience-based details regarding the events in question. The jury later found
the defendant, Gustavo Lopez, guilty of the charges.

14 Lopez appealed, and a split division of the court of appeals affirmed the
judgment of conviction in a published opinion. People v. Lopez, 2024 COA 26, 1 56,
550 P.3d 731, 741. The division agreed with Lopez that Grimm's response to the
juror's question was inadmissible, reasoning that an expert witness may not testify
about the lack of indicia of coaching during a child victim's interview. Id. at | 12,
550 P.3d at 734. Such testimony, explained the division, is analogous to an opinion
about another witness's truthfulness on a particular occasion, which is improper.
Id. But the division nevertheless upheld the trial court's ruling under the opening
the door doctrine. Id. at | 13, 550 P.3d at 734. It determined that the defense had
opened the door to the otherwise inadmissible testimony by persistently
advancing the theory at trial that the children's maternal grandmother wanted to

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keep custody of them and had therefore coached them or otherwise influenced
them "to fabricate the allegations" or form "false memories of abuse." Id. at "[ 23,
550 P.3d at 736. Lopez then sought our review, and we granted his petition.

15 Whether Grimm's answer to the juror's question was admissible is a sticky
wicket, but one on which we do not need to bat today. The question Lopez has
asked us to address revolves around the opening the door doctrine: Whether the
division erred in holding that he opened the door to the challenged expert
testimony. And in Colorado, that doctrine stirs to life only when the evidence in
question is inadmissible.

16 We now affirm. Assuming, without deciding, that the testimony at issue
was inadmissible, we hold that the defense opened the door to it by repeatedly
suggesting to the jury-through both the introduction of evidence and the
presentation of argument-that the children had been coached or otherwise
improperly influenced by their maternal grandmother because she wanted to
maintain custody of them. By consistently attacking the credibility of the children
with assertions that they had been coached, the defense opened the door to
Grimm's testimony that she perceived no indication of coaching.2

2 The question raised by Lopez reads as follows:
Whether a criminal defendant can open the door to expert witness
testimony that another witness told the truth on a particular occasion.

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## I. Facts and Procedural History

17
As relevant here, Lopez was charged with sexual assault by one in a position
of trust and aggravated incest against each of his two young children: N.L. (his
son) and A.L. (his daughter). Two different events gave rise to the charges. First,
on one occasion, Lopez inserted his finger into N.L.'s anus three times while
spanking him. N.L. experienced bleeding and significant pain in his anus the
following day. Second, Lopez drove A.L. to a parking lot, got into the backseat of
the car with her, pulled down his pants, and attempted to place her hand on his
penis. She refused and started crying, so he offered her $100. Because she
continued to refuse, he returned to the front seat. He warned her, however, not to
tell anyone about the incident.

18 Following the children's outcries, Lopez was arrested. Upon seizing his cell
phone, investigators discovered images of prepubescent children in various stages

This framing notwithstanding, as in Liggett v. People, 135 P.3d 725, 732 n.2 (Colo.
2006), we abstain from addressing whether the opening the door doctrine may
ever permit a witness to testify that another witness told the truth on a particular
occasion. That issue is simply not implicated here. Indeed, the division refrained
from tackling it. As the division aptly pointed out, Grimm did not testify that the
children told the truth during their forensic interviews. Instead, she said that she
didn't see any indication of coaching. "This court is not empowered to give
advisory opinions based on hypothetical fact[ual] situations" posed by counsel.
Tippett v. Johnson, 742 P.2d 314, 315 (Colo. 1987).

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of undress. These images depicted some children exposing their genitalia and
others performing sexual acts.

19 Contrary to their outcries, N.L. and A.L. didn't allege any wrongdoing by
Lopez during initial interviews conducted by a social worker. However, each later
made sexual abuse allegations against their father during a forensic interview
conducted by Grimm. The children's testimony at trial was consistent with their
statements to Grimm.

110 The theory of the defense at trial was that the children's maternal
grandmother had coached them or otherwise influenced them to fabricate the
allegations or form false memories of abuse because she wanted to maintain
custody of them. Defense counsel wove this theme throughout the trial, from the
initial ripple to the final wave-introducing it in voir dire, incorporating it into the
opening-statement roadmap, reinforcing it through witness examinations and
testimony, and hammering it home in closing arguments.

111 In support of the defense's theory, counsel advanced multiple arguments:
during the initial interviews conducted by a social worker, when the children
weren't yet living with their grandmother, they did not report any wrongdoing by
Lopez; when the children later disclosed the allegations (during Grimm's forensic
interviews), there was turmoil in the family and the children had been living with
their grandmother for approximately nine months; there were inconsistencies

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within each of the children's statements; there was no physical evidence
supporting the allegations; at the time of Grimm's interviews, the children
admittedly wanted to live with their grandmother rather than with their parents;
not long before Grimm's interviews, the children's mother told their grandmother
that she wanted the children back; and the children were aware that their
grandmother wanted them to report the allegations to Grimm.

112 The People introduced videos of the forensic interviews of N.L. and A.L.
through Grimm. And, in response to direct-examination questions, Grimm
discussed her interviews with the children.

113 Additionally, without objection, the People qualified Grimm as an expert
witness and elicited from her generalized expert opinions on child forensic
interviewing. Grimm educated the jury about the purpose and general structure
of a child forensic interview, techniques she uses to try to obtain an accurate and
complete account of an incident, the concept of suggestibility, the degree to which
outside forces may influence a child's storage and retrieval of a memory, steps to
mitigate the risk of inadvertently influencing a child, and the concept of a child
being coached to say something happened when it didn't actually happen. On the
issue of coaching specifically, Grimm talked about the signs that forensic
interviewers are trained to look for:

[I]f a child is being coached, it is more difficult for them to describe all
the details of what they can hear, what the room looked like, meaning

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what the clothing looked like that they were wearing, exactly what
was said or how they felt in that situation. When a child is coached,
it is typically difficult for them to recall that information because in
coaching a lot of times people aren't telling the child to say all of these
things as well.

114 On cross-examination, Grimm acknowledged that her role in interviewing
N.L. and A.L. was not to make credibility determinations or to investigate whether
anyone had coached them or otherwise improperly influenced them. Further,
Grimm stressed that she was neither opining about the children's character for
truthfulness nor vouching for their credibility during her interviews. Nor, she
explained, could she testify about whether the children were telling their stories
for the first time or the hundredth time when they spoke with her. She also agreed
with defense counsel that her questions were not intended to "get a specific
answer." To the contrary, she reiterated that, consistent with her training, she tried
to avoid suggestive questions. And she recognized that, while she endeavored to
be careful not to influence either child's account of the allegations, she could not
speak about whether people had previously asked the children suggestive
questions.

115 When Grimm had finished answering the lawyers' questions, a juror
submitted a written question for the court to ask her. The juror wanted Grimm to
compare N.L.'s and A.L.'s behaviors during her interviews to those of alleged
child sexual-assault victims she'd interviewed who had been coached: "In your

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expert opinion, was either [N.L.'s] or [A.L.'s] behavior consistent with interviews
where coaching was present?" Defense counsel objected, arguing that the
question called for Grimm to "opine as to [the] credibility of [other] witness[es],"
namely, N.L. and A.L. The People responded that the question was "relevant and
appropriate" because, without objection, Grimm had discussed coaching with the
jury. Besides, noted the People, this was not a question about whether Grimm
believed the children were telling the truth during her interviews; instead, the
question was simply inquiring whether Grimm had observed signs of coaching in
either of the children, an area in which she'd been properly qualified to opine as
an expert.

116 The trial court overruled the objection. It concluded that "[c]oaching is . . .
different ... broader than merely commenting on credibility, which the appellate
court cases frown upon." The court thus relayed the juror's question to Grimm,
and she answered as follows:

In my opinion I don't feel like I saw huge red flags with that or
anything that indicated that because both children were able to
provide very specific experience-based details around the events that
they did talk with me about.

After this exchange, at defense counsel's prodding, Grimm conceded that where,
as in this case, child victims offer varying accounts of the charged incidents, one
possible explanation is that they are not telling the truth.

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117 The jury returned guilty verdicts on all counts. Lopez then appealed. His
primary argument before the division was that the trial court erred in permitting
Grimm to opine that she saw no indication of coaching. This testimony was
inadmissible, contended Lopez, because it vouched for the children's truthfulness
during their forensic interviews.

118 A fractured division affirmed the trial court's ruling on other grounds in a
published opinion. Lopez, 11 30, 56, 550 P.3d at 737, 741. Relying on the decisions
of two other divisions, People v. Bridges, 2014 COA 65, 1 16, 410 P.3d 512, 514-15,
and People v. Heredia-Cobos, 2017 COA 130, 1 17, 415 P.3d 860, 864, the division first
agreed with Lopez that expert witnesses "may not opine that a child was not
coached in making allegations" or even that there were no signs of coaching
during a child's interview. Lopez, 1 12, 550 P.3d at 734. The division noted that it
is now well settled in Colorado that a witness may not testify that another witness
told the truth on a particular occasion. Id. And, in the division's view, the
challenged expert testimony crept too close to testimony about another witness's
truthfulness during an interview and was thus "tantamount to vouching" for that
witness's credibility on a specific occasion. Id. (quoting Heredia-Cobos, 1 14, 415
P.3d at 864).

119 But the division then agreed with the People that, to the extent the expert
testimony at issue was inadmissible, Lopez opened the door to it by continuously

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maintaining that the children's allegations were the product of coaching or
improper influence by identifiable individuals. Id. at 123, 550 P.3d at 736.
Drawing from the analytical map charted in Bridges and Heredia-Cobos, the division
explained that Lopez opened the door to the testimony in question by persistently
advancing the theory that grandmother had coached the children or otherwise
influenced them to fabricate the allegations or form false memories of abuse. Id.
120 The division hastened to add a caveat, however: Simply attacking a child
victim's credibility doesn't open the door to otherwise inadmissible coaching
testimony. Id. at "[ 24, 550 P.3d at 736. Rather, explained the division, the opening
the door doctrine must be narrowly construed to permit such testimony only when
the record establishes "that the defendant 'clearly intended to suggest to the jurors'
that the child had been coached or otherwise improperly influenced by certain
identifiable people." Id. (quoting Heredia-Cobos, "[ 23, 415 P.3d at 866). Because the
division concluded that the record in this case satisfied this condition, it upheld
the trial court's ruling allowing Grimm to answer the juror's question. Id. at [[ 24,
30, 550 P.3d at 736-37.

121 Judge Schutz dissented. He didn't bat an eye at the idea that a defendant in
a criminal case may open the door to testimony about generic behaviors a coached
witness typically manifests. Id. at [ 61, 550 P.3d at 742 (Schutz, J., dissenting).
Consequently, he acknowledged that when a defendant introduces evidence that

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a child victim has been coached, the People are entitled to introduce "expert
testimony explaining what factors the jury should consider" in evaluating whether
the child has been coached. Id. at 1 71, 550 P.3d at 744. But Judge Schutz locked
horns with his colleagues both in the division in Heredia-Cobos and in the division

here on their conclusion that, under the opening the door doctrine, a witness may
testify that a particular child didn't appear to have been coached. Id. In his view,
expert testimony suggesting that a child didn't appear to have been coached, on
the one hand, and expert testimony that a child told the truth, on the other, are the
same dish on a different plate. Id. at 1 72, 550 P.3d at 744-45. And because
everyone agreed that the latter is improper, he asserted that the former must be as
well. Id. Thus, he would not have followed Heredia-Cobos's holding, which he
perceived as too broad and out of sync with our jurisprudence. Id. at 1 67, 550 P.3d
at 743.

## II. Analysis

122 We begin with a brief word about the division's analytical
springboard -anchored in Bridges and Heredia-Cobos-that expert testimony that
a child victim showed no signs of coaching is always inadmissible. This premise
set the stage for the division's application of the opening the door doctrine -a
finding of inadmissibility is the first rung on that ladder. Because the admissibility
question is not before us, however, we quickly set it aside and simply assume,

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without deciding, that Grimm's contested testimony was inadmissible. We
therefore proceed to apply the opening the door doctrine.

123 We ultimately agree with the division that Lopez opened the door to
Grimm's expert testimony that she saw no indication of coaching during her
forensic interviews with N.L. and A.L. Accordingly, we affirm. Before we turn
out the lights, however, we offer two admonitions. First, as the division observed,
the opening the door doctrine must be narrowly construed. Second, the width of
the opening dictates how much the opposing party may carry through it.

## A. A Brief Word on the Division's Admissibility Analysis

124 As noted, the division grounded its admissibility analysis in its sister
divisions' decisions in Bridges and Heredia-Cobos. The division in Bridges
determined, in short order, that the forensic interviewer's expert testimony that
the two child victims had not been coached was just as improper and inadmissible
under CRE 608(a) as expert testimony that a child victim told the truth on a specific
occasion. Bridges, 1 16, 410 P.3d at 514. A few years later, the division in Heredia-
Cobos followed suit; it similarly ruled, again with only a light analytical touch, that
a forensic interviewer's expert testimony about a child victim not showing any
signs of having been coached is just as improper and inadmissible under CRE
608(a) as testimony that a child victim told the truth during an interview. Heredia-
Cobos, T 16, 415 P.3d at 864. Like its predecessors, the division here seemingly

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proceeded on the understanding that our case law had resolved the admissibility
question under review. But the issue is more nuanced than the three divisions
appear to have appreciated.

125 Although it is clear that an expert witness may not directly vouch for the
credibility of a child victim by opining that the child told the truth on a particular
occasion, "the scope . .. of that proposition . .. ha[s] always been somewhat
unclear." Venalonzo v. People, 2017 CO 9, 1 67, 388 P.3d 868, 885-86 (Coats, J.,
concurring in the judgment). And our case law doesn't squarely resolve whether
the ambit of the proposition stretches far enough to sweep in expert testimony
either that a child victim has not been coached or that no signs of coaching were
detected during a child victim's interview.3

3 Compare People v. Snook, 745 P.2d 647, 648 (Colo. 1987) (analyzing the admissibility
of the challenged expert testimony under CRE 608(a), not CRE 702, and
disagreeing with the People that (1) expert "opinion evidence that merely
corroborates a particular person's version of the offense" without directly
vouching for the person's character for truthfulness falls outside the scope of CRE
608(a)'s prohibition, and (2) no abuse of discretion occurred because the expert
testimony did not "explicitly" corroborate the child victim's credibility); People v.
Wittrein, 221 P.3d 1076, 1081-82 (Colo. 2009) (following Snook and applying CRE
608(a) without mentioning CRE 702); and Venalonzo, 11 32, 33, 388 P.3d at 877-78
(adhering to Snook's CRE 608(a) analysis-without determining whether the
testimony was expert opinion evidence subject to CRE 702-in rejecting the
division's conclusion that the testimony that child victims commonly give
conflicting details was proper rebuttal evidence in light of the defense's contention
that the conflicting details were indicia of fabrication; and declaring that testimony
with "direct and indirect implications [about] a child's truthfulness" wanders
outside the evidentiary fence line) (emphasis added)); with People v. Gaffney, 769
P.2d 1081, 1086 (Colo. 1989) (explaining that CRE 608(a) doesn't preclude "all

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126 This is a thorny issue to be sure. But it's one we have no occasion to prune
today.

127 The division agreed with Lopez that the disputed expert testimony was
inadmissible, and the People didn't file a cross-petition to challenge that ruling.
Only Lopez sought review, and the sole question he raised deals with the
division's application of the opening the door doctrine. Of course, had the division
deemed Grimm's challenged testimony admissible, there would have been no
need to summon the opening the door doctrine, and any concerns Lopez and
others may have about the application of the doctrine in this case would have been

statements that may tend to support the credibility of a child-victim's out-of-court
statements or in-trial testimony concerning a sexual crime," and acknowledging
that CRE 702 permits expert testimony establishing that traits, characteristics,
and/or behaviors exhibited by a child victim matched those found in other child
victims of sexual abuse); People v. Fasy, 829 P.2d 1314, 1317-19 (Colo. 1992)
(upholding the admission of expert testimony that (1) the child victim's behaviors
after the sexual assault aligned with those of children suffering from posttraumatic
stress disorder, (2) the child victim suffered from that disorder, and (3) a sexual
assault could have triggered the disorder; rejecting the defendant's reliance on
CRE 608(a); and holding that the challenged expert testimony was admissible
under CRE 702, in part because it helped the jury understand post-incident
behaviors exhibited by the child victim, including the yearslong delay in reporting
the sexual abuse, notwithstanding the fact that such testimony indirectly and
incidentally bolstered the child victim's credibility); and People v. Cooper, 2021 CO
69, 1 97, 496 P.3d 430, 448 (cautioning that generalized expert testimony isn't
rendered inadmissible merely because it has an "incidental" bolstering effect on a
domestic violence victim's credibility; and citing People v. Relaford, 2016 COA 99,
1 30, 409 P.3d 490, 496, for the proposition that "expert testimony generally tends
to bolster or attack the credibility of another witness" (quoting People v. Koon, 724
P.2d 1367, 1370 (Colo. App. 1986)).

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rendered obsolete. Given the current posture of the case, we assume, without
deciding, that the expert testimony in the spotlight was inadmissible and we
accordingly turn our focus to the opening the door doctrine.

## B. Lopez Opened the Door to the Contested Expert Testimony

128 We construe the contours of the opening the door doctrine de novo. See
People v. Johnson, 2021 CO 35, 1 15, 486 P.3d 1154, 1158. However, a lower court's
determination that a party opened the door to otherwise inadmissible evidence is
subject to review for an abuse of discretion. Id. at [ 16, 486 P.3d at 1158. We
likewise review a trial court's decision to admit expert testimony for an abuse of
discretion. People v. Coons, 2021 CO 70, 1 41, 495 P.3d 961, 969.

129 The opening the door doctrine may permit a party to present otherwise
inadmissible evidence after the opposing party has introduced incomplete
evidence that may lead the factfinder astray. See Golob, 180 P.3d at 1012. This
judicially crafted rule serves to prevent a party from getting the upper hand at trial
by selectively presenting facts that create an incorrect or misleading impression.
Id .; see also Miller, 890 P.2d at 98-99 (same). Through the opening the door doctrine,
a party may correct or otherwise place in context any such misimpression by
bringing in evidence that would otherwise be barred. Golob, 180 P.3d at 1012.

130 In Golob, a whodunit case, the parties' experts examined partial shoeprints
collected at the crime scene and compared them to the soles of Golob's boots.

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180 P.3d at 1009. In response to questions on direct examination, the People's
expert testified that he interpreted the conclusion in the defense expert's report to
be consistent with his finding that it was highly probable that Golob's right boot
made one of the prints collected at the crime scene. Id. In support of this
testimony, the People's expert pointed to the defense expert's determination that
the identifying marks on the soles of Golob's boots did not "conclusively match"
the collected prints. Id. According to the People's expert, that determination
meant that the defense expert's comparison fell within " the probable range." Id.
(emphasis added)). Although the defense expert took issue with this
interpretation of his report, he was unable to convey his disagreement to the jury
because, based on the People's objection, the trial court limited his testimony to
the "specific characteristics of Golob's boots" and precluded him from testifying
about his comparison of the prints recovered to the soles of Golob's boots. Id. at
1009, 1012.

131 We agreed with the trial court's decision to exclude the defense expert's
testimony comparing the recovered shoeprints to the known footwear, as he
lacked direct training and experience in that field. Id. at 1012. But we nevertheless
held that the trial court "should have permitted [him] to offer his comparison
testimony because the prosecution opened the door" to it:

By limiting [the defense expert's] testimony, the trial court permitted
the jury to hear only one side of this issue. [The defense expert] was

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unable to explain the means by which he reached his opinion or how
it differed from [the] opinion [offered by the People's expert]. Once
the trial court permitted [the People's expert] to comment on [the
defense expert's] opinion, it should have allowed [the defense expert]
to testify on this subject to provide the full context of the print
evidence to the jury.

Id. at 1012-13. We added that the trial court's ruling allowed the testimony of the
People's expert regarding the defense expert's report "to stand unchallenged and
resulted in an unfair advantage ... through the selective presentation of expert
opinion to the jury on . . . important evidence." Id. at 1013.

132 Taking our cues from Golob, we conclude that the division in this case
correctly ruled that Lopez opened the door to the challenged expert testimony. As
the division discerned, by repeatedly suggesting to the jury -through both the
introduction of evidence and the presentation of argument - that the grandmother
had coached the children or otherwise influenced them to fabricate the allegations
or form false memories of sexual abuse, the defense opened the door to Grimm's
expert opinion that she did not perceive any indication of coaching.

133 In voir dire, defense counsel questioned prospective jurors about the topic
of suggestibility: whether people can sway or influence family members; whether
anyone had had experiences with people taking advantage of others or with
people suggesting to others that something that isn't real is actually real; whether
children are suggestible, prone to being taken advantage of, or susceptible to being
manipulated into believing that something that's not real is actually real; whether

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someone who is close to a child can convince the child to believe that something
that's not real is actually real; and the possible motives someone may have for
attempting to influence a child's perception of reality.

134 Defense counsel went so far as to discuss a "hypothetical" to determine
whether a prospective juror thought that an adult could suggest to a child that
something happened even though it didn't happen. The hypothetical involved a
five-year-old child whose grandmother was living with the child and wanted the
child to stay with her. Before counsel could continue, the court sustained the
People's objection, finding that defense counsel was asking "an improper staking
out question" that included "the facts of the case or the purported facts" of the
case and seeking to ascertain how the prospective juror "would judge" that
scenario.

135 The defense kept the same threads running during its opening statement.
Defense counsel told the jurors that the versions of events they were about to hear
would "differ based on who ha[d] control over the children" at any given time.
Thus, counsel encouraged the jury to pay close attention to the timing of the
children's statements, where the children were "when things [were] happening,"
and who the children were with "when they [were] making these various
allegations."

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136 Counsel further interlaced the defense theme into the fabric of the cross-
examinations of the People's witnesses. For example, the defense introduced
evidence in support of its coaching theory through its questions of A.L. Defense
counsel asked A.L. about her denial of any wrongdoing by Lopez during the social
worker's interview, which occurred before A.L. moved in with her grandmother.
Counsel then juxtaposed that interview with the interview by Grimm, which
occurred after A.L. moved in with her grandmother. Through further questioning,
A.L. conceded the following: that she discussed with her grandmother why she
was going to be interviewed by Grimm and what she planned to say during the
interview; that her grandmother wanted to make sure A.L. would say exactly what
she ended up saying during Grimm's interview; that she spoke to her brother
before Grimm interviewed him, and that she was aware that her brother was also
going to say "some stuff" during that interview; that she wanted to live with her
grandmother; that her grandmother was aware this was her wish; and that her
grandmother likewise wanted to live with her.

137 In similar fashion, the defense introduced evidence in support of its
coaching theory during the cross-examination of N.L. For example, defense
counsel conveyed to the jury that, after moving in with his grandmother, N.L.
recounted a different narrative to Grimm than the one he'd shared with the social
worker. N.L. acknowledged that when he initially spoke to the social worker, he

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didn't mention any inappropriate touching by Lopez. He further admitted that it
was after he moved in with his grandmother that he told Grimm that Lopez had
inappropriately touched him. Moreover, N.L. agreed with defense counsel that:
he talked to his grandmother about Grimm's interview beforehand; his
grandmother wanted to make sure he would tell Grimm what happened; and he
told Grimm that he wanted to live with his grandmother rather than with his
mother or father.

138 Along the same lines, while the children's grandmother was on the stand,
defense counsel suggested that the grandmother threw Lopez under the bus to
keep custody of the children. Specifically, the defense elicited testimony from the
grandmother that she delayed reporting the allegations of abuse for almost a year.
She further agreed with defense counsel that she reported these allegations after
the children's mother announced that she wanted to regain custody of the
children.

139 Next, during the cross-examination of Grimm, the defense presented
evidence that the fact that there were multiple interviews conducted with each
child gave rise to suggestibility concerns. Defense counsel also prompted Grimm
to acknowledge that the children might have discussed the sexual abuse
allegations with many people before their forensic interviews.

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140 At the end of the trial, in closing argument, the defense drummed into the
jurors the theme sowed in voir dire and nurtured throughout the trial. Counsel
argued that the grandmother coached the children or otherwise influenced them
to fabricate the allegations or form false memories.

141 In sum, Lopez defended against the charges in this case by persistently
presenting evidence and argument that the grandmother egged the children on to
fabricate allegations or form false memories. The defense's theory of the case was
that the children changed their initial stories and made unfounded allegations
against Lopez during Grimm's forensic interviews because their grandmother had
coached them or otherwise improperly influenced them. But that was only part of
the story: the defense's telling. The rest of the story was filled in by Grimm, who
opined, in response to a juror's question, that based on both her observations of
N.L.'s and A.L.'s behaviors during her forensic interviews and her comparison of
those behaviors to the behaviors of children she'd observed in cases where
coaching appeared to be present, she detected no indication of coaching here.

142 Given the defense's persistent theme and Grimm's unopposed generalized
expert testimony about coaching, it is hardly surprising that a juror posed the
question at issue: "In your expert opinion, was either [N.L.'s] or [A.L.'s] behavior
consistent with interviews where coaching was present?" The jurors were almost
invited to ask it. In essence, the juror's question sought to have Grimm apply her

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generalized expert opinions -none of which the defense disputed - to the facts of
the case, which is something expert witnesses are routinely permitted to do at trial.
And precluding Grimm from addressing the juror's question would have given
Lopez an unfair advantage by creating a misleading impression.

143 There were, after all, two sides to the coaching coin. The defense's
contention that the children were coached or otherwise improperly influenced by
their grandmother was one side. The other was Grimm's answer to the juror's
question: During her interview of each child, she saw no indication of coaching.
Grimm's response supplied the context necessary to complete the picture the
defense had painted. True, that evidence was prejudicial to Lopez, but our rules
don't prohibit prejudicial evidence. What they prohibit is unfairly prejudicial
evidence. And, in the context of the evidence introduced and arguments
presented by Lopez, there was nothing unfairly prejudicial about Grimm's
challenged expert testimony. Accordingly, we conclude that Lopez opened the
door to it.

## C. Two Admonitions

144 As we come down the home stretch, we feel compelled to part with two
admonitions. First, we wholeheartedly agree with the division that the opening
the door doctrine must be narrowly applied. Lopez, 1 24, 550 P.3d at 736. Lopez
could not have opened the door to the expert testimony at issue simply by

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challenging the child victims' credibility. The door was opened in this case
because defense counsel repeatedly suggested-through the introduction of
evidence and the presentation of argument -that the children had been coached
or otherwise improperly influenced by their grandmother.

145 Second, "[m]erely because a defense attorney opens the door does not mean
that a prosecutor can come storming through it in a pair of hobnailed boots."
United States v. Sepulveda, 15 F.3d 1161, 1189 n.24 (1st Cir. 1993). As Lopez urges,
any evidence admitted under the opening the door doctrine must be limited to
that necessary to remove any unfair prejudice that may have ensued from the
original evidence. See People v. Cohen, 2019 COA 38, 1 23, 440 P.3d 1256, 1262
(stating that the opening the door concept "isn't unlimited"). In other words, the
opening's width must dictate how much the opposing party may pass through it.
146 Here, the record reflects that the People didn't weaponize the door kicked
open by the defense: The defense relentlessly pressed throughout the trial its claim
that the children had been coached or otherwise improperly influenced by their
grandmother, and the People responded through Grimm's opinion that she
perceived no indicia of coaching during her interviews with the children.4 More

4 Nothing in our opening the door jurisprudence fenced the People into a
nonevidentiary response. Nor is there support in Colorado law for the notion that
Lopez, as the party who swung the gate open, was entitled to stand in the doorway

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importantly, the record bears out that the district court didn't abuse its discretion
in permitting Grimm's challenged expert testimony, which was tightly confined
in scope and did nothing to widen the door opened by the defense. See Coons, T
41, 495 P.3d at 98 (noting that we review a trial court's admission of expert
testimony for an abuse of discretion). Appellate courts reviewing for an abuse of
discretion reverse only when the disputed decision "is manifestly erroneous." Id.
(quoting People v. Rector, 248 P.3d 1196, 1200 (Colo. 2011)). This highly deferential
standard keeps an appellate court from second-guessing the trial court's on-the-
ground judgment. Cooper, 1 93, 496 P.3d at 447. With no manifest error in sight in
this case, we have no basis to climb down from the appellate perch and intrude
upon the district court's domain. Instead, our review ends where the district
court's exercise of sound discretion began.

## III. Conclusion

147
For the foregoing reasons, we affirm the division's judgment. We remand
the case to the division with instructions to return it to the district court.

CHIEF JUSTICE MÁRQUEZ, joined by JUSTICE BOATRIGHT and JUSTICE
BLANCO, dissented.

and dictate the form of the evidence the People properly carried across the
threshold.

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CHIEF JUSTICE MÁRQUEZ, joined by JUSTICE BOATRIGHT and JUSTICE
BLANCO, dissenting.

148 Today the majority relies on the "opening the door" doctrine to justify the
admission of otherwise inadmissible expert opinion testimony on the credibility
of child witnesses. It does so in a child sexual assault case, the very kind of case
that frequently hinges on credibility. In so doing, it holds for the first time that a
defendant "opens the door" to such inadmissible (and unfairly prejudicial)
evidence merely by pursuing a garden-variety "coaching" theory of defense that
challenges the credibility of the allegations against the defendant. Here, the
majority does not identify specific testimony introduced by the defense that would
require additional context to correct an objectively misleading impression.
Instead, it holds for the first time that a defendant "opens the door" to the
introduction of otherwise inadmissible expert vouching testimony simply by
pursuing a theory of defense - through voir dire and opening statements (neither of
which are evidence), and even closing arguments (which are not only not
evidence, but which somehow contribute to "opening the door" after the close of
evidence). In short, the majority takes an already confusing and amorphous
doctrine and stretches it beyond recognition.

149 The majority assumes, without deciding, that the expert's testimony was
inadmissible. Maj. op. 16. But this issue should be decided outright. As Judge

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Schutz explained, the testimony at issue here was inadmissible because there is no
principled distinction between testimony that a child "was not coached" and
testimony that a child "was being truthful." People v. Lopez, 2024 COA 26, 1 60,
550 P.3d 731, 741 (Schutz, J., dissenting). In other words, the expert's testimony in
this case was impermissible vouching. See People v. Eppens, 979 P.2d 14, 17-19
(Colo. 1999).

150 Equally importantly, the opening the door doctrine is inapplicable here. As
I explain below, the doctrine comes into play only when one party (1) introduces
testimony that (absent correction or additional context) creates an objectively
misleading inference for the jury and (2) prevents the opposing party from
explaining or rebutting that objectively misleading inference. Because Gustavo
Lopez did neither in this case simply by pursuing his theory of defense, the
doctrine does not apply. In any event, permitting expert opinion testimony
regarding the child victims' truthfulness on specific occasions is a
disproportionate response that injects unfair prejudice, particularly in a case such
as this that hinges on credibility. The majority distorts the doctrine by applying it
here, and in so doing, it effectively deters future defendants from pursuing a
defense that a victim was coached into making false allegations.

[51 For the foregoing reasons, I respectfully dissent.

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## I. The Expert's Testimony Was Inadmissible Because It Concerned Specific Instances of the Children's Truthfulness

152 "In Colorado, neither lay nor expert witnesses may give opinion testimony
that another witness was telling the truth on a specific occasion." People v. Wittrein,
221 P.3d 1076, 1081 (Colo. 2009). Testimony that another witness told the truth
amounts to a credibility determination, which is a matter "solely within the jury's
province." People v. Baker, 2021 CO 29, 1 2, 485 P.3d 1100, 1102; see also Venalonzo v.
People, 2017 CO 9, 1 32, 388 P.3d 868, 877 ("The danger in admitting such testimony
lies in the possibility that it will improperly invade the province of the fact-
finder.").

153 "Testimony that another witness is credible is especially problematic where
the outcome of the case turns on that witness's credibility," a situation that often
arises in child sexual assault cases. Venalonzo, 1 33, 388 P.3d at 877 (emphasis
added). A child's testimony as to abuse has an outsized importance because
children may delay reporting sexual abuse, so collecting physical evidence
becomes difficult or impossible. Id., 388 P.3d at 878. This means that the child's
testimony becomes the most significant evidence in the case. Id.

154 Here, the majority acknowledges that "it is clear that an expert witness may
not directly vouch for the credibility of a child victim by opining that the child told
the truth on a particular occasion." Maj. op. 1 25. Yet that is exactly what

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happened here: By testifying that the children were not coached in a case that
turned on their credibility, the expert directly vouched for their credibility. That is,
the expert's testimony was inadmissible because it concerned specific instances of
the children's truthfulness. See Eppens, 979 P.2d at 17 ("It is well established that
CRE 608(a)(1) does not permit a witness to offer an opinion that a child was telling
the truth on the specific occasion that the child reported a particular sexual assault
by a defendant.").

155 Our precedent on direct vouching leads to this inescapable conclusion. Four
decades ago, in Tevlin v. People, 715 P.2d 338, 339 (Colo. 1986), we considered the
testimony of an expert in child abuse investigation. The expert formed an opinion
as to whether "the victim gave truthful information based on the interviews [the
expert] conducted with the victim and his stepbrother" and then "testified that he
believed the victim was telling the truth about the fact that he was beaten by the
petitioner with the belt." Id. at 340. We held that the expert's testimony ran afoul
of CRE 608 because it went to the victim's truthfulness on a specific
occasion- directly vouching for the child's credibility. Id. at 341; see also People v.
Oliver, 745 P.2d 222, 225 & n.2 (Colo. 1987) (holding that expert witness and lay
witness testimony that "they personally believed each of the three victims, based
upon their experience and interviews of the victims" violated CRE 608(a)).

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156 We subsequently held that testimony analogous to saying a witness told the
"truth" can likewise run afoul of CRE 608(a). Eppens, 979 P.2d at 18. In Eppens, for
example, we held that a social worker's lay testimony that she "felt [the victim]
was sincere" was "tantamount to a statement that she found [the victim] to be
truthful." Id. at 17-18. We found it particularly instructive that "sincerity" was
"virtually synonymous with," and contained within, the definition of "truth." Id.
at 18 (citing Truth, Webster's Third New International Dictionary, Unabridged
(1986), which defined "truth" as "sincerity in character, action, and speech").

157 Here, the expert testified about coaching, a concept inextricably linked with
truthfulness. She explained to the jury that coaching is "when someone is telling
the child to say that didn't happen when it really did or they may be telling the
child to say something happened that actually did not." In other words, the expert
explained to the jury that "coaching" occurs when a child is told to share an
untruthful version of events-i.e., to lie. The expert here also testified that she was
trained to look for signs of coaching. Critically, she then testified that, in her expert
opinion, she did not feel like she saw "huge red flags" or "anything that indicated"
the children were coached because both were "able to provide very specific
experience-based details around the events" they described to her.

158 The expert's own explanation of "coaching" made clear to the jury that signs
of coaching indicate untruthfulness. By testifying that she did not see anything

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that indicated coaching, the expert effectively testified that the children were not
lying when they accused Lopez of sexual assault. Put simply, the expert directly
vouched for the children's credibility. As the division correctly explained,

[A]n expert witness may not opine that a child was not coached in
making allegations, or -because it amounts to the same thing -that
the expert did not see signs of coaching. Coaching testimony is
impermissible because it "constitute[s] conclusions about [the
children's] truthfulness in their respective interviews," and is
"tantamount to vouching for the child[ren]'s credibility."

Lopez, 1 12, 550 P.3d at 734 (alterations in original) (citations omitted) (first quoting
People v. Bridges, 2014 COA 65, 1 16, 410 P.3d 512, 514; and then quoting People v.
Heredia-Cobos, 2017 COA 130, 1 14, 415 P.3d 860, 864).

159 Where, as in this case, an expert who is qualified in child forensic
interviewing and trained to detect coaching in children testifies that a child was
not coached to make accusations, "the jury's only conceivable use of such
testimony would be as support for the complainant's truthful character." People v.
Snook, 745 P.2d 647, 649 (Colo. 1987). Because the expert directly vouched for the
children's credibility, her testimony was inadmissible under CRE 608(a).

## II. The Defense Did Not "Open the Door"

160 Having concluded that the expert's testimony is inadmissible, I now turn to
the question of whether the defense nevertheless "opened the door" to the
testimony by pursuing a theory of defense that the children were coached into
making false allegations. Precisely because the theory of defense did not create an

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objectively misleading impression or give the defense an unfair advantage, the
doctrine is inapplicable here. In any event, permitting the prosecution to introduce
an expert opinion on credibility invaded the province of the jury and injected
unfair prejudice into the case. The majority's holding to the contrary distorts the
doctrine beyond recognition and effectively deters future defendants from
pursuing such a defense.

## A. The Theory of Defense Did Not Create an Objectively Misleading Impression or Give the Defense an Unfair Advantage

161 "The concept of 'opening the door,' not codified in our rules of evidence, is
a court-promulgated curative measure that is not easily defined." People v. Melillo,
25 P.3d 769, 775 (Colo. 2001). We have conceptualized it as "an effort by courts to
prevent one party from gaining an unfair advantage by presenting evidence that,
without being placed in context, creates an incorrect or misleading impression."
Id.

162 The purpose of the doctrine in Colorado is to prevent one side from raising
an objectively misleading adverse inference while simultaneously preventing the
other side from explaining or rebutting that inference. See People v. Miller, 890 P.2d
84, 98-99 (Colo. 1995). Accordingly, the doctrine does not apply unless both of
those conditions are present. Because pursuing a defense theory that a victim was
coached does not, in and of itself, raise an objectively misleading adverse

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inference, and because the prosecution in this case was not prevented from
explaining or rebutting the defense's theory, the opening the door doctrine is
inapplicable here.

163 The origin of the doctrine in Colorado is difficult to pinpoint, but several
early cases outline its foundation. It began as a form of impeachment. For
example, in Medina v. People, 291 P.2d 1061, 1062 (Colo. 1956), we held that a
defendant "opened the door" to the question of whether he had ever owned a
pistol by testifying that he had not. To contradict the defendant's (objectively
misleading) testimony, the prosecution introduced rebuttal testimony that the
defendant had been arrested with a pistol some years earlier. Id. We held that the
defendant "opened the door" to the question of gun ownership, and that a party
may always "present evidence to challenge the credibility of an adverse witness
by proof of independent facts and circumstances inconsistent with his or her
testimony." Id .; see also People v. Cole, 654 P.2d 830, 834 (Colo. 1982) (holding that
the defendant's testimony about not using a knife in a prior fight "opened the door
to the issue of the prior fight" and that "the prosecution was entitled to introduce
competent evidence to explain, refute, or disprove the statement, since the
defendant's credibility was in issue").

164 We later relied on the doctrine to permit the use of otherwise restricted (and
therefore inadmissible) testimony to contradict an objectively misleading

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inference raised by an opponent. In People v. Tenorio, 590 P.2d 952, 957 (Colo. 1979),
for example, officers were permitted to testify on direct examination that they
received a call involving a man of the defendant's description, but not that he was
reported to be drunk and brandishing a weapon. On cross-examination, however,
defense counsel elicited testimony from an officer that he had his gun drawn and
pointed at the defendant as he first approached. Id. at 958. On re-direct
examination, the prosecution asked the officer why his gun was drawn, and the
officer explained that the defendant was reported to have a weapon. Id. We held
that the defense's cross-examination "opened the door" to the restricted testimony
because "[t]he district attorney had a right to explain or rebut any adverse
inferences which might have resulted from that cross-examination question." Id.
In other words, the otherwise restricted testimony was admissible because it
tended to explain the objectively misleading adverse inference raised by the
defense's cross-examination.

165 Similarly, in People v. Sams, 685 P.2d 157, 164 (Colo. 1984), we reiterated that
a defendant may not raise an objectively misleading adverse inference while
simultaneously preventing the prosecution from explaining or rebutting that
inference. See id. at 158, 164 (explaining that the proper remedy for the
prosecution's loss of exculpatory identification evidence was suppression of all
identification evidence, and allowing the defense to inquire into suppressed

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identifications on cross-examination but warning that doing so would "open[] the
door" for the prosecution to elicit additional testimony about the same).

166 Over a decade later, we applied the doctrine to allow the introduction of
other crimes evidence otherwise barred by CRE 404(a). Miller, 890 P.2d at 96, 99.
In Miller, the defendant was charged with possession and distribution of cocaine;
a prosecution witness testified that he made two substantial purchases of cocaine
from the defendant on the charged date. Id. at 87-88, 99. On cross-examination,
the defense adduced testimony that suggested the prosecution witness's
relationship with the defendant was entirely casual and lawful before the charged
date, and that the two men knew each other only informally. Id. at 88, 97-99. On
re-direct examination, the prosecution elicited testimony clarifying that the
prosecution witness had bought cocaine from the defendant "quite a few" times
even before the charged date. Id. at 88-90, 97. We held that the defense "open[ed]
the door" to evidence of the defendant's other crimes by seeking "to exclude the
inadmissible evidence that would place that relationship in its proper context,
revealing the true nature and scope of the friendship." Id. at 99. We thereby
reiterated that the defendant could not selectively present facts that created a
factually incorrect or misleading impression while simultaneously preventing the
prosecution from explaining or providing context to correct the misimpression
created by the defense.

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167 Thus, in Miller, we articulated for the first time the rule for "opening the
door" as we use it today: "This concept of 'opening the door' represents an effort
by courts to prevent one party in a criminal trial from gaining and maintaining an
unfair advantage by the selective presentation of facts that, without being
elaborated or placed in context, create an incorrect or misleading impression." Id. at
98-99 (emphases added) (first citing Sams, 685 P.2d at 164; and then citing Tenorio,
590 P.2d at 958).

168 In concluding that the defense "opened the door" in this case, the majority
relies on Golob v. People, 180 P.3d 1006 (Colo. 2008). Maj. op. 132. But Golob rested
on the same principles advanced in Tenorio, Sams, and Miller.5 In Golob, the
prosecution elicited testimony from its expert witness that characterized the
defense expert's findings as consistent with his own findings. 180 P.3d at 1012.
When the defense expert attempted to disagree, the prosecution objected, and the
trial court excluded the defense expert's testimony. Id. at 1009, 1012. We held that

5 Golob did not directly cite to Tenorio, Sams, or Miller; it instead cited People v.
Murphy, 919 P.2d 191, 195 (Colo. 1996), which in turn cited Tenorio, Sams, and
Miller. Golob, 180 P.3d at 1012. But Golob uses the same language as Miller to
describe the opening the door doctrine. Compare Golob, 180 P.3d at 1012
(""[O]pening the door' represents an effort by courts to prevent one party in a
criminal trial from gaining and maintaining an unfair advantage by the selective
presentation of facts that, without being elaborated or placed in context, create an
incorrect or misleading impression."), with Miller, 890 P.2d at 98-99 (same).
Therefore, Golob rested on the same principles as those advanced in Tenorio, Sams,
and Miller.

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the prosecution "opened the door" to the defense expert's testimony because,
otherwise, the prosecution expert's testimony stood unchallenged and "resulted
in an unfair advantage to the prosecution through the selective presentation of
expert opinion to the jury on this important evidence." Id. at 1012-13.

169 The principle we followed in Golob, though applied in a new context, was
nothing new: A party may not mislead the jury into believing objectively untrue
facts. In Tenorio, for example, the concern was that the jury might have believed
that the police officer drew and pointed his gun at the defendant for no reason,
when in fact, the defendant reportedly had a weapon. See Tenorio, 590 P.2d at 958.
In Miller, the concern was that the jury might have found it unlikely that the
defendant would suddenly sell substantial quantities of cocaine to a person he
knew only casually, when in fact, the defendant had sold cocaine to him several
times before. See Miller, 890 P.2d at 99. And in Golob, the concern was that the jury
might have believed that the defense expert's report aligned with the prosecution
expert's report, when in fact, the defense expert disagreed with that
characterization. See Golob, 180 P.3d at 1012-13.

170 Here, however, nothing about the theory of defense misled the jury to
believe objectively untrue facts. It is the jury's role as factfinder to assess the
credibility of witnesses at trial. As is often the situation in child sexual assault
cases, the defense theory challenged the allegations against Lopez by focusing on

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the children's credibility. The majority admits as much. Maj. op. 1 6 ("By
consistently attacking the credibility of the children with assertions that they had
been coached, the defense opened the door .... " (emphasis added)). Unlike the
objectively misleading testimony animating this court's concerns in Tenorio, Miller,
and Golob, the children's credibility in this case was a core issue for the jury to
decide. In exercising its crucial role as factfinder, the jury might have believed the
children's allegations, or it might have believed that the grandmother coached or
otherwise improperly influenced the children because she wanted to maintain
custody of them. Indeed, several aspects of the case arguably undermined the
children's credibility: They initially denied the allegations, their forensic
interviews were delayed, their testimony contained inconsistencies, there was no
physical evidence of either incident, and they had an incentive to make up
allegations against Lopez because they wanted to live with their grandmother. I
also find it especially troubling that the majority treats the theory of defense in this
case as presenting a "misleading impression." Id. at [ 42. I do not see how a
garden-variety theory of defense centered on challenging the credibility of the
allegations against the defendant constitutes "getting the upper hand at trial by
selectively presenting facts." Id. at | 29.

171 Importantly, the defense did not prevent the prosecution from explaining
or rebutting the coaching theory. After the defense engaged in lines of questioning

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on cross-examination to suggest that the children were coached, the prosecution
could, and did, rebut those suggestions on re-direct examination. As just one
example, the defense elicited testimony from the grandmother on cross-
examination that she did not report the incidents to Social Services until after the
children's mother tried to regain custody-suggesting that the grandmother
fabricated the allegations to maintain custody of the children. But on re-direct
examination, the prosecution (appropriately) elicited testimony that the
grandmother did not report the incidents because she thought Social Services
already knew. Because the theory of defense in this case did not create an
objectively misleading adverse inference that could be corrected only by the
introduction of otherwise inadmissible vouching testimony, the opening the door
doctrine does not apply.

## B. Permitting the Expert's Testimony Injected Unfair Prejudice

172 Even if a party "opens the door" to inadmissible evidence, not all
inadmissible evidence may come in. As the majority acknowledges, id. at
TT 44-45, the doctrine allows inadmissible evidence only to the extent necessary
to remove any unfair prejudice, i.e., by correcting an objectively misleading
impression. Permitting the prosecution to present an expert opinion on a child
witness's credibility exceeds these limits and instead injects unfair prejudice into
the case.

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173 Experts are, and should be, permitted to educate jurors about typical
behaviors of children who have been sexually assaulted. People v. Fasy, 829 P.2d
1314, 1317 (Colo. 1992) (holding that expert testimony was admissible where the
expert testified that child sexual assault victims can suffer posttraumatic stress
disorder and that the child victim suffered posttraumatic stress disorder).
However, experts are not permitted to testify that a child was telling the truth
about having been sexually assaulted. People v. Gaffney, 769 P.2d 1081, 1088 (Colo.
1989) (holding that expert testimony was inadmissible where the expert testified
that the child's description of the events was "very believable"); see also Snook,
745 P.2d at 648-49 (holding that expert testimony was inadmissible where the
expert testified that children tend not to fabricate erotic experiences).

174 To the extent the expert's testimony in this case helped the jury to
understand the concept of coaching and described the signs of coaching, it was
proper. For example, the expert testified,

[I]f a child is being coached, it is more difficult for them to describe all
the details of what they can hear, what the room looked like, meaning
what the clothing looked like that they were wearing, exactly what
was said or how they felt in that situation. When a child is coached,
it is typically difficult for them to recall that information because in
coaching a lot of times people aren't telling the child to say all of these
things as well.

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It would have been entirely proper for the jury to take that expert's explanation
and apply it to the evidence in the case, such as the children's video recorded
interviews. But it was entirely improper for the expert to do the jury's work for it.
175 As Judge Schutz explained, jurors often feel saddled with the heavy
responsibility of determining witnesses' credibility. Lopez, 1 60, 550 P.3d at 741
(Schutz, J., dissenting). This responsibility can feel particularly heavy in child
sexual assault cases, "which are emotionally charged and present serious
consequences for both the defendant and the alleged victims." Id. "Facing such
pressures, there is a real risk that jurors may displace their burden to assess
credibility by deferring to the opinion of a purported expert." Id. Those dangers
are precisely why expert testimony about a witness's credibility is prohibited.

176 Notably, the prosecution specifically requested in a motion in limine that all
witnesses be precluded from commenting on other witnesses' veracity, and it
avoided asking the expert to opine directly on the children's truthfulness. Instead,
the expert's testimony vouching for the children's credibility was elicited by a
question from a juror after the prosecution completed its re-direct examination.
177 Permitting the expert to answer the juror's question was manifestly
improper because it was inadmissible vouching testimony that was wholly
unnecessary: The expert's testimony (and other evidence) in the case did not create

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an objectively misleading impression that required correction. As such, allowing
the expert to answer the juror's question was a clear abuse of discretion.

178 The majority asserts that the expert's testimony merely "supplied the
context necessary to complete the picture the defense had painted." Maj. op. 1 43.
But the expert in this case did more than supply "context": She directly vouched
for the children's credibility by effectively testifying that they told the truth when
they accused the defendant of sexual assault. Such testimony was tantamount to
an expert opinion on the children's credibility.

179 Vouching testimony is uniquely harmful because it directly usurps the role
of the jury. Baker, TT 2, 45, 485 P.3d at 1102, 1109. As we have explained,
"[t]estimony that another witness is credible is especially problematic where the
outcome of the case turns on that witness's credibility," and "[t]his often occurs in
child sex assault cases." Venalonzo, 1 33, 388 P.3d at 877. When a child delays
reporting sexual abuse, collecting physical evidence may be difficult or
impossible, and the child's testimony will likely be the most significant evidence
in the case. Id., 388 P.3d at 878. Because the case will turn on whether the jury
finds the child credible, "courts must be particularly mindful of testimony that a
child victim is telling the truth when that child's testimony is 'the focal issue in the
case."" Id. (quoting Snook, 745 P.2d at 649).

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180 The opening the door doctrine "can be used only to prevent prejudice; it
can't be used as an excuse to inject prejudice into the case."" People v. Ray, 2025 CO
42M, 1 86, 575 P.3d 400, 427-28 (emphases added) (quoting People v. Cohen, 2019
COA 38, 1 23, 440 P.3d 1256, 1262-63). The doctrine "isn't unlimited and
'inadmissible rebuttal evidence "is permitted 'only to the extent necessary to
remove any unfair prejudice which might otherwise have ensued from the original
evidence."""" Id., 575 P.3d at 427 (quoting Cohen, 1 23, 440 P.3d at 1262).

181 In this case, there was no physical evidence, and the children's forensic
interviews were delayed. The children's testimony was therefore the most
significant evidence, and the case turned on whether the jury found the children
credible. Permitting an expert to vouch for the children's credibility was thus
inherently unfairly prejudicial because it usurped the jury's role in determining a
key disputed issue in the case. See People v. Kembel, 2023 CO 5, 1 53, 524 P.3d 18,
29 (explaining that unfairly prejudicial evidence has an "adverse effect upon a
defendant beyond tending to prove the fact or issue that justified its admission
into evidence" (quoting United States v. Gilliam, 994 F.2d 97, 100 (2d Cir. 1993)));
People v. Dist. Ct., 785 P.2d 141, 147 (Colo. 1990) (defining unfairly prejudicial
evidence as having "an undue tendency to suggest a decision on an improper
basis").

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## C. The Majority Significantly Expands the Boundaries of the Doctrine

182 Importantly, the majority's holding today significantly expands the use of
the opening the door doctrine by applying it for the first time to a theory of
defense.

183 The majority reasons that Lopez's theory of defense at trial "opened the
door" by "repeatedly suggesting to the jury" that the children were coached and
weaving "this theme throughout the trial, from the initial ripple to the final
wave-introducing it in voir dire, incorporating it into the opening-statement
roadmap, reinforcing it through witness examinations and testimony, and
hammering it home in closing arguments." Maj. op. 11 10, 32.

184 We have never considered counsel's comments made during voir dire,
opening statements, and closing arguments6-none of which are evidence-to
"open the door" to the introduction of otherwise inadmissible evidence, and we
should decline to do so here. Pernell v. People, 2018 CO 13, 11 4, 24, 411 P.3d 669,
670, 673 (declining to address whether an opening statement "opened the door"
to inadmissible evidence); see also Davis v. People, 2013 CO 57, TT 2, 12, 310 P.3d 58,
59, 61.

6 The majority does not explain how the defense's closing arguments, which
obviously occurred after the close of evidence, contributed to "opening the door"
to the expert's testimony here.

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185 In Medina, we held that the prosecution could contradict the defendant's
testimony with lay testimony on rebuttal. 291 P.2d at 1062. In Tenorio, Sams, and
Miller, we held that the prosecution could contradict the defense's cross-
examination with further questioning on re-direct.7 Tenorio, 590 P.2d at 957-58;
Sams, 685 P.2d at 164; Miller, 890 P.2d at 99. And in Golob, we held that the defense
could contradict the prosecution's expert testimony with its own expert testimony.
180 P.3d at 1012-13.

186 But "[o]pening statements are not evidence, and they do not constrain later
argument or introduction of evidence." Davis, 133, 310 P.3d at 65-66 (Bender, C.J.,
concurring in the judgment) ("What is inappropriate, however, is permitting
opposing counsel to present irrelevant or otherwise inadmissible evidence on the
basis that an opening statement, which carries no evidentiary weight, opened the
door to its admission."). The majority's holding in this case stands not only for the
remarkable proposition that a defendant may "open the door" to expert testimony
that a victim was truthful but also that a defendant may "open the door" to such
otherwise inadmissible evidence merely by pursuing a theory of defense "that the
[victim] had been coached or otherwise improperly influenced." Maj. op. 1 44.

7 Even in Venalonzo, a more recent case applying the opening the door doctrine, we
held that the prosecution could contradict the defense's cross-examination of a non-
expert investigating officer with further questioning on re-direct examination.
T 44, 388 P.3d at 880.

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187 I am deeply concerned about the implications of the majority's holding on
future, similarly situated defendants. Coaching is a common defense to
allegations of sexual assault on a child, and the majority's decision today
undercuts any such defense. A defendant who seeks to defend against allegations
of sexual assault on a child by explaining that a third party improperly induced
the child's outcry may now anticipate the introduction of expert testimony
vouching for the child's truthfulness. Indeed, going forward, defendants must be
careful not to even suggest that a child victim might be told what to say-not in
voir dire, opening statement, or closing argument -lest they "open the door" to
expert testimony that the child told the truth. I cannot support this result.

## III. Conclusion

188 By applying the opening the door doctrine to this case, the majority distorts
it beyond recognition. Nothing about Lopez's theory of defense created an
objectively misleading impression or gave the defense an unfair advantage. And
in any event, permitting an expert to directly vouch for the victims' credibility was
a disproportionate response that injected unfair prejudice into a case that hinged
on credibility.

189
89 For the foregoing reasons, I respectfully dissent.