When should Utah courts grant a mistrial for improper testimony? State v. Deprey Explained

In State v. Deprey, the Utah Court of Appeals addressed when trial courts should grant mistrials after witnesses provide improper testimony that was meant to be excluded from the jury. The case provides important guidance for practitioners handling bifurcated trials and dealing with inadvertent disclosure of prejudicial evidence.

Background and Facts

Lucas Deprey shot and killed a suspected drug dealer in a parking lot, claiming the victim had threatened him and reached across his body during their encounter. After fleeing to Oregon, Deprey was arrested and gave incriminating statements during police interrogation. The trial court bifurcated the charges, trying the murder and obstruction counts to the jury while reserving the gun possession charge for the bench to avoid prejudicing the jury with evidence of Deprey’s felon status.

During trial, a detective inadvertently testified that Deprey “made a comment later in the interview that he’s a felon and isn’t allowed to carry a gun.” Defense counsel moved for a mistrial, arguing the improper testimony fundamentally prejudiced the proceedings despite the bifurcation order.

Key Legal Issues

The court addressed multiple issues: (1) whether the trial court abused its discretion in denying the mistrial motion; (2) whether Deprey’s interrogation statements should have been suppressed based on alleged Miranda violations; and (3) whether a flawed jury instruction on extreme emotional distress constituted plain error or ineffective assistance of counsel.

Court’s Analysis and Holding

The Court of Appeals affirmed, applying the principle that “a mistrial is strong medicine” requiring high deference to trial courts. The court found no abuse of discretion because the improper statement was not intentionally elicited, was made in passing, was isolated, and did not interfere with Deprey’s actual defense strategy of self-defense rather than extreme emotional distress. The court distinguished cases where improper testimony directly undermined the defendant’s core defense theory.

Regarding the Miranda claims, the court held that Deprey’s ambiguous references to counsel did not constitute clear invocation of his right to an attorney, and that the detective’s warnings adequately conveyed his right to remain silent despite not using verbatim Miranda language.

Practice Implications

This decision reinforces that mistrials remain extraordinary remedies. When bifurcating charges to exclude prejudicial evidence, practitioners should thoroughly prepare witnesses about prohibited testimony and consider requesting preliminary jury instructions. The court’s analysis also demonstrates the importance of developing and arguing defenses consistently—Deprey’s failure to pursue extreme emotional distress at trial undermined his appellate arguments about prejudicial jury instructions.