RT Journal Article SR Electronic T1 Commentary: Deceptions to the Rule on Ultimate Issue Testimony JF Journal of the American Academy of Psychiatry and the Law Online JO J Am Acad Psychiatry Law FD American Academy of Psychiatry and the Law SP 22 OP 25 VO 34 IS 1 A1 Slovenko, Ralph YR 2006 UL http://jaapl.org/content/34/1/22.abstract AB Federal Rule of Evidence 704(b) (and state counterparts) bars opinion testimony on the effect of mental state on an element of a crime or defense. The application of the rule involves substantial judicial discretion. As the jurisprudence to date indicates, deceptions to the rule circumvent its application.