Testerman v. Wyoming: Limits on Unnoticed 404(b) Evidence & Contextual Review of Vouching

Introduction

Gabriel Lee Testerman v. State of Wyoming, 2025 WY 58, decided May 23, 2025 by the Wyoming Supreme Court, reaffirms the distinction between evidentiary error and prosecutorial misconduct, clarifies the procedure for unnoticed Rule 404(b) evidence, and underscores the contextual approach to alleged prosecutorial vouching. The appellant, a former highway patrol trooper, was convicted of first-degree sexual assault related to an incident with his former girlfriend (CM). He appealed, claiming (1) admission of eight categories of prior-bad-acts evidence without proper notice; (2) improper vouching by the prosecutor; and (3) cumulative errors depriving him of a fair trial. The Court affirmed the conviction and sentence, refining Wyoming’s approach to each issue.

Summary of the Judgment

The Wyoming Supreme Court addressed three critical points:

Unnoticed Rule 404(b) Evidence. Of the eight categories Testerman challenged, five were conceded or found to be Rule 404(b) evidence that had not been the subject of a pretrial Gleason hearing. The Court held that in such circumstances the proper remedy is to review for prejudice under harmless‐error principles rather than apply the abuse-of-discretion standard anew. None of the five items—photographs while CM was blindfolded, testimony that Testerman “kept dirt” on others, his involvement in partner-swapping “Body Snatchers” group, his admission of past marital misconduct, and CB’s testimony about him drinking and driving—prejudiced the verdict.
Prosecutorial Misconduct / Vouching. Two contested statements in closing argument were alleged vouching: praise for Detective Morgan (“he did a good job, he was honest, spilled the beans”) and urging the jury to “believe them” (the victims) because they were believable. The Court held neither statement constituted improper vouching when viewed in context of the prosecutor’s overall argument, jury instructions, and evidence.
Cumulative Error. Even if each error were assumed, their cumulative effect did not deprive Testerman of a fair and impartial trial.

Analysis

1. Unnoticed 404(b) Evidence: Prejudice, Not Automatic Reversal

Wyoming Rule of Evidence 404(b) prohibits admission of “other crimes, wrongs, or acts” merely to show character conformity, but allows such evidence for specific purposes (motive, intent, knowledge, absence of mistake, etc.) provided the prosecution gives reasonable notice and the trial court conducts a Gleason analysis (Gleason v. State, 2002 WY 161).

Key holdings:

When the State gives pretrial notice under Rule 404(b) but later elicits additional prior-bad-acts evidence not covered by the pretrial order, those new items are still subject to review—but only for prejudice under the harmless-error standard. This avoids imposing an impossible burden on trial judges to reconvene Gleason hearings mid-trial for every off-hand mention.
Unobjected-to testimony that does not fit within Rule 404(b) (e.g., CM’s accounts of discussions in the presence of their children or Testerman’s childhood abuse) is reviewed for plain error.
Under Dixon v. State, 2019 WY 37, and related authority, to constitute prejudicial error the mistaken admission must have created a reasonable probability of a more favorable outcome for the defendant.

Application to Testerman: Five categories were conceded as unnoticed 404(b) evidence. The Court applied the five-factor harmless-error analysis (see King v. State, 2023 WY 36) and found none materially prejudiced the outcome. They were either brief background detail, cumulative of defense testimony, or unrelated to the charged first-degree sexual assault.

2. Prosecutorial Vouching: Contextual, Not Isolated, Review

Prosecutorial misconduct requires an improper act that “deprive[s] the defendant of the right to a fair trial” (McGinn v. State, 2015 WY 140). Vouching occurs when the prosecutor offers his personal belief in a witness’s credibility, risking undue weight due to the prosecutor’s perceived authority. Wyoming precedent (e.g., Guy; Dysthe) distinguishes between improper personal attestations and permissible inferences drawn from admitted evidence.

Testerman’s challenges:

Detective Morgan praise: “He did a good job. He was honest, spilled the beans.” The Court held this was not vouching but an invitation to view Morgan’s forthright admissions as evidence—analogous to Burton v. State (1999).
“Believe them.” Urging jurors to believe the victims because they “opened the bedroom door,” not due to #MeToo or gender, but because they were believable. The Court found no improper personal attestation of credibility; instead, the prosecutor directed jurors back to the evidence and reminded them of their sole role in assessing credibility.

Neither comment, in context of the prosecutor’s full closing, jury instructions, and defense arguments, constituted plain or reversible error.

3. Cumulative Error Doctrine

Even a series of individually harmless errors can rise to reversible cumulative error if they so undermine the trial’s fairness that the conviction cannot stand (Hamilton v. State, 2017 WY 72). Here, with no single prejudicial error and no pattern of misconduct, the combined effect of admitted unnoticed 404(b) items and contested closing remarks did not prejudice Testerman’s right to a fair trial. The Court reaffirms that a defendant must show the accumulated errors had a material and unjust impact on the verdict.

Precedents Cited

Gleason v. State, 2002 WY 161, 57 P.3d 332 – Four-part test for admitting 404(b) evidence and pretrial notice requirement.
King v. State, 2023 WY 36, 527 P.3d 1229 – Distinction between evidentiary error and prosecutorial misconduct; harmless-error analysis for unnoticed 404(b).
Dixon v. State, 2019 WY 37, 438 P.3d 216 – Harmless-error standard for prior-bad-acts testimony.
Dysthe v. State, 2003 WY 20, 63 P.3d 875 – Improper vouching when prosecutor personally guarantees witness credibility.
Burton v. State, 1999 WY 119, 46 P.3d 312 – Permissible inference from evidence vs. personal attestation.
White v. State, 2003 WY 163, 80 P.3d 642 – Contextual review of closing argument; no vouching when prosecutor re-directs to evidence and jury instructions.

Legal Reasoning

The Court’s analysis hinges on two core principles:

Functionality of Rule 404(b): Prior bad acts evidence carries inherent prejudice. Wyoming’s mandatory Gleason procedure and pretrial notice mitigate that risk. When evidence sneaks past those safeguards, the proper remedy is harmless-error review, not automatic reversal.
Limits on Vouching: Prosecutors may highlight inferences from evidence but must avoid personal attestations that a witness is credible. Context—entire argument, jury instructions, and adversarial clarity—controls whether comments overstep.

Impact on Future Cases

This decision clarifies that:

Trial courts need not reopen full Gleason hearings mid-trial for every off-notice reference; appellate courts will assess prejudice instead.
Prosecutorial misconduct claims based on 404(b) breaches require showing deprivation of a fair trial, not merely admission of the evidence.
Vouching challenges demand contextual analysis; isolated quotes will not prevail absent clear personal assurances of credibility.

Practitioners should carefully frame 404(b) notices, lodge timely objections, and use curative instructions when prior-bad-acts evidence slips through. Prosecutors should couch credibility arguments in terms of the evidence and jury’s role, avoiding “I know” or “I guarantee” formulations.

Complex Concepts Simplified

404(b) Evidence: Evidence of other acts isn’t allowed just to say “he’s a bad guy.” It can be used to show motive, intent, or lack of accident if the State warns the defense ahead of time and the judge weighs its fairness.
Gleason Hearing: A private conference where the judge decides if the proposed bad-acts evidence really fits one of the permitted reasons and isn’t too unfair.
Harmless Error vs. Plain Error: If you object at trial and the judge admits unfair evidence, on appeal you show it likely changed the outcome (“prejudice”). If you didn’t object, you must show a clear rule was broken and you were greatly harmed.
Vouching: When a prosecutor says “trust me, this guy is honest,” the jury might see the prosecutor as an expert. That’s improper. They can argue from the facts—“she looked you in the eye and told her story”—but not “I know she’s telling the truth.”

Conclusion

Testerman v. State of Wyoming reinforces the careful balance between admitting relevant prior conduct and protecting the jury from unfair prejudice. It clarifies that unnoticed Rule 404(b) evidence is reviewed for harmlessness, not automatic reversal, and that prosecutorial vouching claims must be assessed in context. The decision ensures trial courts retain discretion, appellants bear the burden to show prejudicial impact, and prosecutors maintain wide but principled latitude in closing arguments. The judgment thus stands as a clear guidepost for the handling of “other‐acts” evidence and credibility arguments in Wyoming’s criminal trials.