Plaintiff Colleen Nix alleged that Kevin Keiner, a New Mexico State Police Officer, sexually assaulted her while she was intoxicated and asleep.
Nix sought to introduce the testimony of both Elizabeth Thomson and Andrea Taylor. New Mexico Department of Public Safety and New Mexico State Police requested the Court to bar Thomson and Taylor from testifying.
Law Enforcement Expert Witness
Elizabeth Thomson is a retired law enforcement professional with more than two decades of experience. From 1999 to 2017, Thomson served as an officer with the Albuquerque Police Department (“APD”), retiring at the rank of sergeant. She held a variety of investigative and supervisory roles at APD.
Psychology Expert Witness
Andrea Brooke Taylor is a licensed clinician and retired law enforcement captain with over 20 years of experience in trauma-focused mental-health counseling. She has a Masters Degree in Clinical Mental Health Counseling and a Masters Degree in Forensic Psychology. She specializes in Post Traumatic Stress Disorder (“PTSD”), Complex Post-Traumatic Stress Disorder (“CPTSD”), trauma assessment, and the psychological impact of sexual violence.
Discussion by the Court
Elizabeth Thomson
Thomson is qualified based on her twenty years of law enforcement experience and extensive training. For instance, she may testify regarding patterns in sexual assault cases due to her training, field experience, and six years of specialized service on a crisis intervention team. She may testify regarding police procedures based on her service as a homicide sergeant, where she developed and updated departmental policies and standard operating procedures.
Defendants sought to limit Thomson’s testimony. First, they challenged her opinions regarding Nix’s and Keiner’s credibility as usurping the jury’s role. Specifically, they sought to preclude Thomson from testifying that Nix was truthful while Keiner was not, or from characterizing the parties’ statements as “consistent” or “inconsistent.”
Nix contended that Thomson did not make credibility determinations but instead applied her investigative expertise to identify “consistencies and inconsistencies” in the parties’ statements. The Court is not persuaded. Even when framed in these terms, such testimony effectively invites the jury to conclude that accounts deemed “consistent” are credible, while those labeled “inconsistent” are not.
Next, Defendants sought to preclude Thomson from testifying that the evidence is consistent with a nonconsensual sexual encounter. The Court declined to limit such testimony. Expert testimony offering “general and conditional opinions” about whether behavior aligns with patterns observed in sexual abuse cases is permissible.
Finally, Defendants moved to preclude Thomson from testifying that Keiner was acting under “color of law” because such testimony would usurp the role of the jury. In this case, the Court found that Thomson’s proposed testimony—that Keiner was acting under “color of law” when he encountered Nix—did not usurp the jury’s fact-finding role. Jurors are unlikely to understand how police officers are trained to recognize whether they are acting under “color of law.”
Andrea Taylor
A. Taylor’s methodology is reliable under 702
First, Keiner argued that Taylor’s methodology is unreliable under Rule 702. Taylor’s opinions are the product of a reliable methodology. She employed a multi-method approach to screen Nix for PTSD and CPTSD by administering seven diagnostic questionnaires and conducting two clinical interviews.
The Court found Keiner’s arguments to the contrary unpersuasive. First, he argued that Taylor’s opinions are unreliable because she failed to use a Clinician-Administered PTSD Scale (“CAPS-5”) to diagnose Nix with PTSD “despite acknowledging CAPS-5 as the gold standard.” As discussed above, Taylor’s methodology is reliable because it is grounded in her professional experience.
Next, Keiner challenged Taylor’s conclusion that Nix has Complex PTSD because “Complex PTSD is not a distinct diagnosis under the DSM-5.” Taylor sufficiently explained each step of her analysis and the basis for her conclusions. The Court’s inquiry ends there.
Keiner also argued that Taylor’s opinions are unreliable because she failed to perform any differential etiology or rule out alternative causes of Plaintiff’s PTSD symptoms. The Court disagreed. Differential etiology is simply one method of assessing causation in the medical context. Keiner’s assertion that Rule 702 “requires an expert to engage in a reasoned differential etiology” is unsupported. Regardless, Taylor accounts for alternative causes of Nix’s symptoms and distinguishes between Nix’s baseline functioning and her post-incident decline. Taylor acknowledged Nix’s pre-existing anxiety and extensive trauma history, including childhood abuse and prior violence.
B. Taylor’s methodology is based on sufficient facts and data under 702
Keiner next argued that Taylor’s opinions are not based on sufficient facts or data under Rule 702.
Taylor relied on sufficient facts and data here. She concluded, “to a reasonable degree of psychological certainty,” that the alleged sexual assault caused Nix’s PTSD and CPTSD symptoms. Taylor based that opinion on Nix’s “test results, symptom presentation, personal narrative, and trauma chronology,” and testified that her methodology was “standard” and grounded in her professional experience. The Court is satisfied that Taylor did not selectively “cherry pick” favorable facts but relied on the type of information reasonably considered by mental-health professionals conducting trauma assessments.
Keiner claimed that Taylor improperly relied on Nix’s self-report without “independently verifying” the information through medical or therapy records, the Sexual Assault Nurse Examiner (“SANE”) exam, or other “objective” evidence. But the Court does not “require every expert to undertake an independent evaluation of the entire record to determine what he or she did or did not need to consider.” Taylor testified that it is “standard” to rely on self-reported symptoms to form diagnostic opinions—that is all the Court requires under 702.
C. Portions of Taylor’s testimony are unhelpful under 702
Finally, Keiner argued that portions of Taylor’s proposed testimony are not “helpful” under Rule 702. Specifically, Keiner challenged Taylor’s assertions that Nix was truthful in reporting the alleged assault; trauma victims “have no gain” in being untruthful; and gaps in Nix’s deposition testimony can be explained by dissociation or freezing.
Taylor may not vouch for Nix’s truthfulness at trial. Taylor may not testify, for example, that Nix was truthful in reporting the incident or that inconsistencies in Nix’s account resulted from a trauma response. Those determinations remain within the exclusive province of the jury. The Court also barred Taylor from opining that trauma victims “have no gain” in being untruthful—such testimony crosses the line into improper bolstering by suggesting that the jury should accept Nix’s account.
This limitation did not preclude Taylor from testifying about the experiences and behaviors of trauma victims generally.
Held
- The Court granted in part and denied in part Defendants’ motion to exclude Elizabeth Thomson.
- The Court granted in part and denied in part Defendants’ motion to exclude Andrea Taylor.
Key Takeaway
Expert testimony offering “general and conditional opinions” regarding patterns commonly observed in sexual-abuse victims is admissible. Taylor may testify, for example, that sexual-assault victims may experience memory lapses, dissociation, and freezing responses. Such testimony assists jury members in evaluating Nix’s testimony without telling them what to believe—an important distinction under 702.
Case Details:
| Case Caption: | Nix V. New Mexico Department Of Public Safety |
| Docket Number: | 1:24cv691 |
| Court Name: | United States District Court, New Mexico |
| Order Date: | May 27, 2026 |
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