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111 Va. L. Rev. Online 1 (2025)

handle is hein.journals/inbrf111 and id is 1 raw text is: COPYRTGHT © 2025 VIRGTNTA LAW RRVTRW ASSOCTATTON VIRGINIA LAW REVIEW ONLINE VOLUME 111 JANUARY 2025 1-13 COMMENT MODUS OPERANDI AND MINDREADING IN DIAZ v. UNITED STATES Isaiah Affron* INTRODUCTION Witnesses with the requisite knowledge or expertise often present, as an opinion, their answer to a case's ultimate issue. They may opine, say, that a product was unreasonably dangerous in a product liability suit, or that a patent was infringed in a patent infringement suit, or that damages of a certain amount are appropriate, even if the jury is tasked with answering that same question.1 This principle is unambiguously announced in Rule 704(a) of the Federal Rules of Evidence. It reads: An opinion is not objectionable just because it embraces an ultimate issue.2 The Rules feature only one caveat, articulated in Rule 704(b): In a criminal case, an expert witness must not state an opinion about whether the defendant did or did not have a mental state or condition that constitutes an element of the crime charged or of a defense.3 In other * J.D., University of Virginia School of Law, expected 2026. Thank you to Professors Charles Barzun and Rachel Bayefsky for their feedback on an earlier draft. Many thanks, also, to Amy Vanderveer and the editors of the Virginia Law Review for their contributions to this Comment. 1 6 Michael H. Graham, Handbook of Federal Evidence § 704:1 (9th ed. 2023). There is no comprehensive list of all possible ultimate issues. See 29 Charles Alan Wright & Victor Gold, Federal Practice and Procedure § 6284, at 469 (2d ed. 2016). 2 Fed. R. Evid. 704(a) (emphasis added). 3 Fed. R. Evid. 704(b). 1