State v. C. Byrne, 2021 MT 238

Byrne was tried and convicted by a jury in Powell County of three counts of felony sexual intercourse without consent with a child under 12; the alleged conduct occurred 2009–2011 and the victim (M.G.) was 15 at trial.
Before trial Byrne obtained a motion in limine (stipulated by the State and granted by the court) barring the State from eliciting testimony that directly vouched for M.G.’s credibility or asking experts whether they believed her.
Despite the stipulation, the prosecutor elicited testimony from four witnesses (a child-abuse expert and three clinicians/forensic interviewer) that tended to bolster M.G.’s truthfulness or downplay coaching/malicious reporting; the prosecutor also told the jury in closing that M.G. was a “reliable witness.”
The case was essentially a credibility contest: no physical evidence, no eyewitnesses to the assaults, and the verdict depended on whether jurors believed M.G. over Byrne’s denial.
Byrne appealed arguing the State breached the limine stipulation and improperly vouched for the victim; the Supreme Court of Montana reversed and remanded for a new trial.

Issue	Plaintiff's Argument (State)	Defendant's Argument (Byrne)	Held
Whether Byrne preserved his prosecutorial-misconduct claim despite not objecting at each occurrence	Plain-error standard should apply; there was no definitive adverse ruling and Byrne failed to contemporaneously object	Motion in limine (stipulated and granted) preserved the issue; contemporaneous objections would be redundant	Court: preserved — the State stipulated and the court granted the motion in limine, so Byrne’s claim was preserved for appeal
Whether eliciting expert/lay testimony that bolstered M.G.’s credibility and the prosecutor’s closing comment denied Byrne a fair trial	Testimony was educational/benign, any error was harmless given the testimony and other circumstantial corroboration; jury instructions cured any prejudice	The State reneged on its stipulation; multiple witnesses and the prosecutor improperly vouched for M.G., cumulatively prejudicing Byrne in a credibility-driven case	Court: reversible error — cumulative improper vouching by witnesses plus prosecutor’s personal comment that M.G. was a “reliable witness” undermined a fair trial; conviction reversed and remanded

State v. Scheffelman, 250 Mont. 334, 820 P.2d 1293 (narrow exception allowing an expert to opine on a very young child-victim’s credibility when properly qualified and specific foundation exists)
State v. Grimshaw, 2020 MT 201, 401 Mont. 27, 469 P.3d 702 (expert testimony implying low false-report rates improperly bolstered victim credibility in a he-said/she-said case)
State v. Brodniak, 221 Mont. 212, 718 P.2d 322 (expert testimony on statistical frequency of false accusations is improper comment on victim credibility)
State v. Stringer, 271 Mont. 367, 897 P.2d 1063 (prosecutor’s personal opinions on witness truthfulness usurp the jury’s role and are reversible error)
State v. Partin, 287 Mont. 12, 951 P.2d 1002 (prosecution’s breach of stipulation/motion in limine prejudicial where evidence against defendant is weak; reversal appropriate)
State v. Sinz, 2021 MT 163, 404 Mont. 498, 490 P.3d 97 (permitting general, non-credibility-directed testimony from a child-abuse expert when the expert reiterates not to opine on the victims’ credibility)
State v. Hensley, 250 Mont. 478, 821 P.2d 1029 (limits on expert testimony about credibility; exception narrow and fact-specific)
State v. Robins, 2013 MT 71, 369 Mont. 291, 297 P.3d 1213 (distinguishing direct credibility opinions from permissible background/educational expert testimony)