§ Rule 705. Disclosure of facts or data underlying expert opinion

Codes > Pennsylvania Statutes and Consolidated Statutes > Rules of > Article VII > Rule 705.

Rule 705. Disclosure of facts or data underlying expert opinion

The expert may testify in terms of opinion or inference and give reasons therefor; however, the expert must testify as to the facts or data on which the opinion or inference is based.

Comment: The text and substance of Pa.R.E. 705 differ significantly from F.R.E. 705. The Federal Rule generally does not require an expert witness to disclose the facts upon which an opinion is based prior to expressing the opinion. Instead, the cross-examiner bears the burden of probing the basis of the opinion. Pennsylvania does not follow the Federal Rule. See Kozak v. Struth, 515 Pa. 554, 560, 531 A.2d 420, 423 (1987) (declining to adopt F.R.E. 705, the Court reasoned that “requiring the proponent of an expert opinion to clarify for the jury the assumptions upon which the opinion is based avoids planting in the juror's mind a general statement likely to remain with him in a jury room when the disputed details are lost.”) Relying on cross examination to illuminate the underlying assumption, as F.R.E. 705 does, may further confuse jurors already struggling to follow complex testimony. Id.

Accordingly, Kozak requires disclosure of the facts used by the expert in forming an opinion. The disclosure can be accomplished in several ways. One way is to ask the expert to assume the truth of testimony the expert has heard or read. The Kroeger Co. v. W.C.A.B., 101 Pa. Cmwlth. 629, 516 A.2d 1335 (1986); Tobash v. Jones, 419 Pa. 205, 213 A.2d 588 (1965). Another option is to pose a hypothetical question to the expert. Dietrich v. J.I. Case Co., 390 Pa. Super. 475, 568 A.2d 1272 (1990); Hussy v. May Department Stores, Inc., 238 Pa. Super. 431, 357 A.2d 635 (1976).

The salient facts relied upon as the basis of the expert opinion must be in the record so that the jury may evaluate the opinion. See Commonwealth v. Rounds, 518 Pa. 204, 542 A.2d 997 (1988). The expert's testimony regarding the facts or data on which the opinion is based is subject to Pa.R.E. 703.