In Diaz v. United States, 144 S.Ct. 1727 (2024), a divided court held that expert testimony in a criminal case, as to whether “most people” in the defendant’s position have a particular mental state, does not run afoul of Federal Rule of Evidence 704(b)’s prohibition against expert opinion evidence about whether a criminal defendant had or lacked the mental state required for conviction. Particularly in white-collar cases, where the defendant’s intent is often the central disputed issue, the implications of Diaz may be far-reaching.
This presentation will explore the background and contours of Rule 704(b), examine Diaz and other decisions relevant to the Rule, and consider defense strategies in a post-Diaz landscape.