Federal Rules of Evidence – Rule 704 (through March 1, 2020)
Generally, experts can opine about ultimate issues, like whether a defendant shot the sheriff. But experts can never opine about a criminal defendant’s mental state if that mental state is an element of a charged crime or relevant defense, like malice in a murder case.
(a) In General — Not Automatically Objectionable. An opinion is not objectionable just because it embraces an ultimate issue.
(b) Exception. 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. Those matters are for the trier of fact alone.
Selected Committee Notes
The basic approach to opinions, lay and expert, in these rules is to admit them when helpful to the trier of fact. In order to render this approach fully effective and to allay any doubt on the subject, the so-called “ultimate issue” rule is specifically abolished by the instant rule.
The older cases often contained strictures against allowing witnesses to express opinions upon ultimate issues, as a particular aspect of the rule against opinions. The rule was unduly restrictive, difficult of application, and generally served only to deprive the trier of fact of useful information. 7 Wigmore §§1920, 1921; McCormick §12. The basis usually assigned for the rule, to prevent the witness from “usurping the province of the jury,” is aptly characterized as “empty rhetoric.” 7 Wigmore §1920, p. 17. Efforts to meet the felt needs of particular situations led to odd verbal circumlocutions which were said not to violate the rule. Thus a witness could express his estimate of the criminal responsibility of an accused in terms of sanity or insanity, but not in terms of ability to tell right from wrong or other more modern standard. And in cases of medical causation, witnesses were sometimes required to couch their opinions in cautious phrases of “might or could,” rather than “did,” though the result was to deprive many opinions of the positiveness to which they were entitled, accompanied by the hazard of a ruling of insufficiency to support a verdict. In other instances the rule was simply disregarded, and, as concessions to need, opinions were allowed upon such matters as intoxication, speed, handwriting, and value, although more precise coincidence with an ultimate issue would scarcely be possible.
Many modern decisions illustrate the trend to abandon the rule completely. People v. Wilson, 25 Cal.2d 341, 153 P.2d 720 (1944), whether abortion necessary to save life of patient; Clifford-Jacobs Forging Co. v. Industrial Comm., 19 Ill.2d 236, 166 N.E.2d 582 (1960), medical causation; Dowling v. L. H. Shattuck, Inc., 91 N.H. 234, 17 A.2d 529 (1941), proper method of shoring ditch; Schweiger v. Solbeck, 191 Or. 454, 230 P.2d 195 (1951), cause of landslide. In each instance the opinion was allowed.
The abolition of the ultimate issue rule does not lower the bars so as to admit all opinions. Under Rules 701 and 702, opinions must be helpful to the trier of fact, and Rule 403 provides for exclusion of evidence which wastes time. These provisions afford ample assurances against the admission of opinions which would merely tell the jury what result to reach, somewhat in the manner of the oath-helpers of an earlier day. They also stand ready to exclude opinions phrased in terms of inadequately explored legal criteria. Thus the question, “Did T have capacity to make a will?” would be excluded, while the question, “Did T have sufficient mental capacity to know the nature and extent of his property and the natural objects of his bounty and to formulate a rational scheme of distribution?” would be allowed. McCormick §12.