Commonwealth v. Quinn

This case requires us to examine the line that separates permissible expert testimony regarding the behavioral characteristics of sexually abused children from impermissible expert testimony that implicitly vouches for the credibility of the victim witness. Because we conclude that the prosecutor in this case, over objection, elicited expert testimony during cross-examination of the victim’s therapist that crossed that line, and because we conclude that the error was prejudicial, we vacate the defendant’s convictions and remand for a new trial.

Background. A Superior Court jury convicted the…