Colo. R. Evid. 705
The expert may testify in terms of opinion or inference and give reasons therefor without first testifying to the underlying facts or data, unless the court requires otherwise. The expert may in any event be required to disclose the underlying facts or data on cross-examination.
(Federal Rule Identical.)
CRE 705
Committee Comment
Although the present rule is contrary to Colorado case law, the Committee believes it to be the better view. The reasons for the retention of the proposed Federal rule as it is presently written are as follows. First, the rule does not disturb the requirement for a proper foundation for expert opinions. City and County of Denver v. Lyttle, 106 Colo. 157, 103 P.2d 1 (1940). Secondly, the elimination of the requirement for preliminary disclosure of underlying facts or data has the effect of reducing the need for hypothetical questions, a goal which has been sought by a number of states. Thirdly: "If the objection is made that leaving it to the cross-examiner to bring out the supporting data is essentially unfair, the answer is that he is under no compulsion to bring out any facts or data except those unfavorable to the opinion. The answer assumes that the cross-examiner has the advance knowledge which is essential for effective cross-examination. This advance knowledge has been afforded, though imperfectly, by the traditional foundations requirement." Advisory Committee's Notes, Proposed Federal Rules. See also, Archina v. People, 135 Colo. 8, 307 P.2d 1083 (1957). Finally, it is clear that there is built-in safeguard in the discretionary power of the court to require prior disclosure.
Annotation Law reviews. For article, "Opinion Testimony", see 22 Colo. Law. 1185 (1993). For article, "Cross-Examining and Impeaching Expert Psychiatric Witnesses", see 26 Colo. Law. 75 (November 1997). Cross-examination concerning basis of opinion permitted. It is fundamental that an expert witness may be cross-examined concerning the basis of his opinion. People v. Alward, 654 P.2d 327 (Colo. App. 1982), cert. dismissed, 677 P.2d 948 (Colo. 1984); People v. Diefenderfer, 784 P.2d 741 (Colo. 1989). Although this rule provides that the expert "may in any event be required to disclose the underlying facts or data on cross-examination", this principle is not absolute. When the expert has testified in summary fashion, the counsel of this rule is that the court should allow wide latitude for cross-examination. However, the trial judge may certainly impose reasonable limits upon the cross-examination, and he should cut off the attack where its purpose is to support the cross-examiner's case by bringing out inadmissible hearsay rather than simply to undermine the expert's opinion. People v. Diefenderfer, 784 P.2d 741 (Colo. 1989). Medical experts are allowed to state the bases of their opinions. Where there exist various possible causes of an injury and the burden of proving causation rests on the plaintiffs, defendant's experts should be allowed to state their opinions and articulate the bases of their opinions in detail, as did plaintiffs' experts. Thirsk v. Ethicon, Inc., 687 P.2d 1315 (Colo. App. 1983). Applied in Stone v. Caroselli, 653 P.2d 754 (Colo. App. 1982).