The
Federal Rules of Evidence adopted in 1975 (and their state counterparts) expressly allowed
expert testimony to include statements on ultimate issues if such statements will be helpful to the judge or jury. In 1984, Federal Rule of Evidence 704(b) was added following the trial of
John Hinckley Jr. for the
attempted assassination of U.S. President Ronald Reagan. The changes were in part a result of the public
backlash due to Hinckley's successful use of the
insanity defense. These changes, in particular Rule 704(b), put limits on expert witness testimony. The new rules of evidence restrict the testimony allowed on the ultimate issue. Rule 704(b) states that in criminal actions, the mental health expert may testify to the defendant's
mental disorder or defect and its symptoms, but may not offer a conclusion on an ultimate issue such as the sanity or insanity of the defendant. The expert witness must refrain from merely giving the jury a conclusion that pertains to the legal issues at hand and cannot testify to legal conclusions (ultimate issues), the rationale being that mental health professional are not attorneys. The rationale for this restriction was stated in the legislative history of the rule as the following: For example, the
Third Circuit Court of Appeals in
United States v. Rutland ruled that testimony from "an extraordinarily qualified handwriting expert" was admissible on the "ultimate issue of authorship of key documents". ==Jeffrey R. MacDonald trial==