Section 703. Bases of an Expert’s Opinion Testimony

An expert may base an opinion on facts or data in the case that the expert has been made aware of or personally observed. If experts in the particular field would reasonably rely on those kinds of facts or data in forming an opinion on the subject, they need not be admissible for the opinion to be admitted.

Comment

This rule is identical to the first two sentences of F.R.E. 703. It does not include the third sentence of the Federal Rule that provides that the facts and data that are the bases for the expert’s opinion are not admissible unless their probative value substantially outweighs their prejudicial effect. This is inconsistent with Pennsylvania law which requires that facts and data that are the bases for the expert’s opinion must be disclosed to the trier of fact. See Pa.R.E. 705.

Pa.R.E. 703 requires that the facts or data upon which an expert witness bases an opinion be ‘‘of a type reasonably relied upon by experts in the particular field. . . .’’ Whether the facts or data satisfy this requirement is a preliminary question to be determined by the trial court under Pa.R.E. 104(a). If an expert witness relies on novel scientific evidence, Pa.R.C.P. No. 207.1 sets forth the procedure for objecting, by pretrial motion, on the ground that the testimony is inadmissible under Pa.R.E. 702, or Pa.R.E. 703, or both.

When an expert testifies about the underlying facts and data that support the expert’s opinion and the evidence would be otherwise inadmissible, the trial judge upon request must, or on the judge’s own initiative may, instruct the jury to consider the facts and data only to explain the basis for the expert’s opinion, and not as substantive evidence.

An expert witness cannot be a mere conduit for the opinion of another. An expert witness may not relate the opinion of a non-testifying expert unless the witness has reasonably relied upon it in forming the witness’s own opinion. See, e.g., Foster v. McKeesport Hospital, 260 Pa. Super. 485, 394 A.2d 1031 (1978); Allen v. Kaplan, 439 Pa. Super. 263, 653 A.2d 1249 (1995).

Official Note

Adopted May 8, 1998, effective October 1, 1998; Comment revised September 11, 2003, effective September 30, 2003; rescinded and replaced January 17, 2013, effective March 18, 2013.

Committee Explanatory Reports:

Final Report explaining the September 11, 2003 revision of the Comment published with the Court’s Order at 33 Pa.B. 4784 (September 27, 2003).

Final Report explaining the January 17, 2013 rescission and replacement published with the Court’s Order at 43 Pa.B. 651 (February 2, 2013).

The provisions of this Rule 703 amended September 11, 2003, effective September 30, 2003, 33 Pa.B. 4784; rescinded and replaced January 17, 2013, effective in sixty days, 43 Pa.B. 620. Immediately preceding text appears at serial pages (303516) and (299643).