§ Rule 703. Bases of opinion testimony by experts
Rule 703. Bases of opinion testimony by experts
The facts or data in the particular case upon which an expert bases an opinion or inference may be those perceived by or made known to the expert at or before the hearing. If of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence.
Comment: Pa.R.E. 703 differs from F.R.E. 703 as discussed below. Pa.R.E. 703 is consistent with prior Pennsylvania case law.
F.R.E. 703 was amended on December 1, 2000, to add a balancing test that tilts against disclosure to a jury of otherwise inadmissible facts or data upon which an expert witness bases his or her opinion. In Pennsylvania, however, Pa.R.E. 705 requires an expert witness to testify as to the facts or data upon which the witness's opinion is based, whether or not the facts or data would otherwise be admissible in evidence.
Historically, Pennsylvania courts limited the facts or data upon which an expert could base an opinion to those obtained from firsthand knowledge, or from substantive evidence admitted at trial. See, e.g. Collins v. Hand, 431 Pa. 378, 246 A.2d 398 (1968); Murray v. Siegal, 413 Pa. 23, 195 A.2d 790 (1963). In the case of Commonwealth v. Thomas, 444 Pa. 436, 282 A.2d 693 (1971), the Pennsylvania Supreme Court adopted a rule that allows a medical expert witness to offer an opinion that is based, in part, on otherwise inadmissible hearsay, if it is of a type that is customarily relied on by the expert in the practice of the expert's profession.
Later case law expanded the evidential ruling in the Thomas case to various non-medical expert witnesses. See, e.g., Steinhauer v. Wilson, 336 Pa. Super. 155, 485 A.2d 477 (1984) (expert on construction costs); Maravich v. Aetna Life & Casualty Co., 350 Pa. Super. 392, 504 A.2d 477 (1986) (fire marshal); Kearns v. DeHaas, 377 Pa. Super. 392, 546 A.2d 1226 (1988) (vocational expert); In re Glosser Bros., 382 Pa. Super. 177, 555 A.2d 129 (1989) (tax accountant); Commonwealth v. Bowser, 425 Pa. Super. 24, 624 A.2d 125 (1993) (accident reconstruction expert).
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 shall or on his 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. Cases hold that it is error for an expert witness to relate the opinion of a non-testifying expert unless the witness has reasonably relied upon it, in part, 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).