Plata County District Court No. 14CR457 Honorable William L.
J. Weiser, Attorney General, Elizabeth Ford Milani, Assistant
Attorney General, Denver, Colorado, for Plaintiff-Appellee
A. Ring, Colorado State Public Defender, Stephen Arvin,
Deputy State Public Defender, Denver, Colorado, for
1 Sexual assault cases are particularly difficult given the
need to balance the rights of the victim against those of the
accused. See State v. Boisvert, 400 A.2d 48, 51
(N.H. 1979). The law must weigh the consequences of invading
the accuser's privacy and the related risk that sexual
assaults may go unreported if victims fear embarrassment or
intimidation. At the same time, the defendant's rights to
a fair trial and to challenge the credibility and veracity of
the accuser must be protected.
2 The Colorado General Assembly, like other legislatures
throughout the United States, enacted a rape shield statute
§ 18-3-407, C.R.S. 2018 (the Rape Shield Statute) to
strike this balance.
3 This case presents that dilemma. We must decide whether the
trial court properly balanced a defendant's efforts to
challenge the truthfulness of the accuser against the
prosecutor's evidence bolstering the accuser's
credibility. We conclude that it did not.
4 Defendant, Edmund Peter Marx, appeals his convictions of
sexual assault on a child (position of trust as part of
pattern of abuse), sexual assault on a child (position of
trust), and aggravated incest. The accuser alleged that Marx
had sexually assaulted her on multiple occasions when she was
5 Marx's defense focused on the accuser's alleged
lack of credibility. The prosecutor responded by calling an
expert witness to provide opinions on the likelihood that a
child or teenager will falsely report a sexual assault and
the prevalence of sexual assault.
6 Marx contends that the trial court erred by:
• allowing the prosecutor to introduce expert testimony
on the percentage of children and teenagers who fabricate
allegations of sexual abuse, the percentage of girls who are
sexually abused by family members, and the percentage of
women who have been sexually assaulted;
• excluding a neighbor's testimony challenging the
accuser's truthfulness; and
• rejecting the defense's request for an evidentiary
hearing under the Rape Shield Statute, to determine whether
Marx could introduce at trial evidence of the accuser's
purported history of falsely accusing schoolmates of sexual
7 We hold that Marx is entitled to a new trial because the
trial court erred by permitting the prosecutor's expert
to provide the statistical opinions; that the trial court
correctly excluded the neighbor's testimony; and that the
trial court erred by not conducting a hearing on the
admissibility of Marx's evidence allegedly showing that
the accuser had falsely reported sexual assaults.
Trial Court Erred in Admitting the Expert's Statistical
Expert's Opinions on Sexual Assault Statistics
8 The prosecutor called Sheri Vanino as an expert on
"sexual assault victim behavior." The trial court
accepted her as an expert. Vanino told the jury that
"between 2 and 8 percent of sexual assaults that are
reported to the police turn out to be false. For a child . .
. the studies are more around 2 to 6 percent, child or teen .
. . ." She further testified that sexual assault is
"not at all rare. One in four women are [sic] sexually
assaulted in a lifetime, most of whom are sexually assaulted
under the age of 18." She noted that "somewhere
around 50 percent of children . . . are abused by a family
Standard of Review
9 We review a trial court's ruling on the admissibility
of expert testimony for an abuse of discretion. Kutzly v.
People, 2019 CO 55, ¶ 8, 442 P.3d 838, 841. A court
abuses its discretion when its decision is manifestly
arbitrary, unreasonable, or unfair, or when it misconstrues
the law. People v. Salas, 2017 COA 63, ¶ 30,
405 P.3d 446, 453.
10 The parties dispute whether Marx preserved his objections
to Vanino's opinion testimony. We need not decide the
preservation issue, however, because we hold that the
testimony was improper even under the plain error standard of
11 Plain error is error that is obvious and substantial.
Hagos v. People, 2012 CO 63, ¶ 14, 288 P.3d
116, 120. An error is "obvious" if the challenged
action contravened a clear statutory command, a well-settled
legal principle, or Colorado case law. People v.
Pollard, 2013 COA 31M, ¶ 40, 307 P.3d 1124, 1133. A
"substantial" error is one that so undermined the
fundamental fairness of the trial itself as to cast
"serious doubt on the reliability of the judgment of
conviction." Id. at ¶ 43, 307 P.3d at 1133
(quoting Hagos, ¶ 14, 288 P.3d at 120).
12 "Because this standard was formulated to permit an
appellate court to correct 'particularly egregious
errors,' the error must impair the reliability of the
judgment of conviction to a greater degree than under
harmless error to warrant reversal." Hagos,
¶ 14, 288 P.3d at 120 (quoting Wilson v.
People, 743 P.2d 415, 420 (Colo. 1987)).
Expert Testimony on Whether Children Tend to Fabricate Sexual
Abuse Allegations and the Likelihood of Becoming a Victim of
13 An expert witness may provide opinion testimony so long as
"the expert's specialized knowledge will assist the
jury in understanding the evidence or in determining a fact
in issue." People v. Mintz, 165 P.3d 829, 831
(Colo.App. 2007). An expert may not opine on a witness's
credibility or that a witness was telling the truth on a
specific occasion. People v. Wittrein, 221 P.3d
1076, 1081 (Colo. 2009) (citing People v. Eppens,
979 P.2d 14, 17 (Colo. 1999)); see United States v.
Sanchez-Lima, 161 F.3d 545, 548 (9th Cir. 1998)
("Testimony regarding a witness' credibility is
prohibited unless it is admissible as character
14 Thus, "experts may not offer their direct opinion on
a child victim's truthfulness or their opinion on whether
children tend to fabricate sexual abuse allegations."
Wittrein, 221 P.3d at 1081. Expert testimony that
children tend not to fabricate stories of sexual abuse is
"tantamount to [an expert] testifying that [a] child
victim was telling the truth about her allegations."
Id. at 1082 (citing People v. Snook, 745
P.2d 647, 648 (Colo. 1987)).
15 Although expert testimony is not permitted to bolster a
victim's credibility, an expert may testify concerning
whether a sexual assault victim's behavior or demeanor
was consistent with the typical behavior of victims of abuse.
People v. Glasser, 293 P.3d 68, 78 (Colo.App. 2011).
This type of testimony is admissible because it assists the
jury in understanding the victim's behavior after the
incident and explains why the victim acted the way he or she
did. People v. Relaford, 2016 COA 99, ¶ 28, 409
P.3d 490, 496. "Background data providing a relevant
insight into the puzzling aspects of the child's conduct
and demeanor which the jury could not otherwise bring to its
evaluation . . . is helpful and appropriate in cases of
sexual abuse of children . . . ." Id. (quoting
People v. Whitman, 205 P.3d 371, 383 (Colo.App.
2007)). Although this type of testimony "necessarily
carrie[s] with it the implication that the child's report
of sexual abuse was true," it is proper expert testimony
because it "aid[s] the jury in understanding the
typicality of reactions by young [victims] who have been
subjected to sexual abuse that might, under other
circumstances, be considered bizarre." Id. at
¶ 30, 409 P.3d at 496 (quoting People v.
Morrison, 985 P.2d 1, 6 (Colo.App. 1999)).
16 The admissibility of opinion testimony that assists the
jury in understanding a victim's behavior, however, does
not mean "that testimony of general characteristics of
any type is admissible to attack or support a witness's
credibility." Id. at ¶ 31, 409 P.3d at 496
(quoting People v. Cernazanu, 2015 COA 122, ¶
20, 410 P.3d 603, 606-07). Rather, opinion testimony of
general characteristics is admissible only if it "(1)
relates to an issue apart from credibility and (2) only
incidentally tends to corroborate a witness's
Expert's Testimony on Whether Children and Teenagers Tend
to Fabricate Sexual Abuse Allegations Was an Impermissible
17 Vanino's testimony regarding the small percentage of
children and teenagers who make false allegations of sexual
assault improperly bolstered the accuser's credibility.
Vanino's opinion that only two to six percent "of
sexual assaults that are reported to the police [by children
and teenagers] turn out to be false" did not relate to
any issue other than the accuser's truthfulness. The
practical result of Vanino's testimony was to suggest to
the jury that the accuser was "almost certainly telling
the truth." See Snook, 745 P.2d at 649.
18 Vanino could have explained the typical demeanor and
behavioral traits of a sexually abused child or teenager,
which would have allowed the jury to gain a better
understanding of the accuser's actions after Marx
allegedly sexually assaulted her. See Relaford,
¶ 32, 409 P.3d at 496; cf. Morrison, 985 P.2d
at 6 ("[S]ubstantially all of th[e] expert's
testimony was properly received . . . to aid the jury in
understanding the typicality of reactions by [children] who
have been subjected to sexual abuse."). This type of
testimony would not have told the jurors what result to reach
and thus would have been permissible. See Relaford,
¶ 33, 409 P.3d at 496.
19 But Vanino's testimony about the percentage of
children and teenagers who fabricate sexual assault
allegations did not serve any purpose other than to attempt
to influence the jurors' determination of the
accuser's credibility. See id. at ¶ 34, 409
P.3d at 496; see also Snook, 745 P.2d at 649
("[T]he jury's only conceivable use of [the]
testimony would be as support for the [victims'] truthful
character[s]."). The testimony did not aid the jury in
deciding the case because it did not provide information
whether, in this case, the allegations of sexual
assault were truthful. See Relaford, ¶ 31, 409
P.3d at 496.
Expert's Testimony on the Likelihood of Becoming a Victim