State v. Black, 437 P.3d 1121

Background

Defendant was convicted after a trial in which Dr. Johnson, a psychologist, was precluded from testifying about whether the prosecutors’ interviews of two witnesses (GP and JN) complied with established forensic-interviewing protocols.
The trial court allowed Johnson to testify generally about proper interview techniques (open-ended questions, avoiding leading/suggestive/emotionally coercive prompts, and exploring alternative hypotheses/secondary gain) but barred him from applying those standards to the specific interviews in the case, citing the vouching rule.
Johnson adhered to the court’s limitation at trial; he did not opine on whether GP’s or JN’s statements were truthful or on the specifics of those interviews.
On appeal the Court of Appeals affirmed, holding that applying the standards to the specific interviews would be tantamount to impermissible vouching for/against witness credibility.
The Oregon Supreme Court granted review, held that applying an expert’s methodology-based critique to particular interviews is not necessarily vouching, and concluded the trial court erred by excluding Johnson’s proffered applied testimony.
The Court reversed the conviction and remanded, finding the exclusion was not harmless because the excluded testimony related to central issues and was not merely cumulative of other evidence.

Issues

Issue	State's Argument	Defendant's Argument	Held
Whether expert testimony applying established interview protocols to case-specific interviews is impermissible vouching	Such applied testimony implicitly opines on witness credibility and risks usurping the jury’s role; exclusion was proper	Applied critique provides tools for jurors to evaluate credibility; it is not an opinion that a witness is truthful/untruthful and therefore is admissible	Trial court erred: testimony critiquing specific interviews (shortcomings vs protocols) is not per se vouching and can be admissible; exclusion on vouching grounds was improper
If not vouching, whether the testimony should have been excluded under OEC 702/403 (helpfulness vs prejudice)	The testimony would add little aid beyond what jurors could deduce and risked improperly influencing them; trial court’s limitation was justified	The testimony was helpful and nonduplicative; it would identify concrete protocol deviations the interviewers denied or minimized	Court: admissibility under OEC 702/403 must be separately assessed; record showed trial court did not exercise that discretion, so exclusion cannot be upheld on those grounds
Whether error in excluding Johnson’s applied testimony was harmless	Exclusion was harmless: other testimony and cross-examination already showed potential flaws; defendant’s theory was broader	Exclusion was prejudicial because the critique was central to defendant’s challenge to the investigation and not fully developed by other witnesses	Court: error was not harmless — testimony related to central issues and was not merely cumulative; reversal warranted
Proper analytical framework for vouching objections to expert testimony	Emphasize balancing helpfulness and implicit credibility effects (discretionary, OEC 702/403 lens)	Categorical rule: exclude only testimony that expresses an opinion about truthfulness; otherwise allow testimony that supplies tools for jurors	Court: clarify two-step approach — first ask if testimony conveys an opinion about truthfulness (vouching); if not, then evaluate admissibility under OEC 702/403.

Key Cases Cited

State v. Milbradt, 305 Or. 621 (inadmissible where expert opined a victim did not display deception indicators)
State v. Keller, 315 Or. 273 (inadmissible where expert’s statements effectively asserted child was credible)
State v. Middleton, 294 Or. 427 (admissible expert testimony describing typical victim behavior that helped jurors assess credibility)
State v. Beauvais, 357 Or. 524 (distinguishing permissible evaluative testimony from impermissible vouching; integrate OEC 702/403 analysis)
State v. Southard, 347 Or. 127 (diagnosis of child sexual abuse unsupported by physical evidence inadmissible under OEC 702/403)
State v. Lupoli, 348 Or. 346 (evaluative criteria underlying a diagnosis may be inadmissible when diagnosis itself is excluded under Southard)
State v. Chandler, 360 Or. 323 (discussing purpose and scope of vouching rule)
State v. Viranond, 346 Or. 451 (detective’s testimony that witnesses’ trial testimony was consistent with prior statements was admissible and not automatically vouching)