Tenn. R. Evid. 703
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. Facts or data that are otherwise inadmissible shall not be disclosed to the jury by the proponent of the opinion or inference unless the court determines that their probative value in assisting the jury to evaluate the expert's opinion substantially outweighs their prejudicial effect. The court shall disallow testimony in the form of an opinion or inference if the underlying facts or data indicate lack of trustworthiness.
Tenn. R. Evid. 703
Advisory Commission Comments.
Experts in the field may base opinions on facts not in evidence under this rule. Requisite foundations are that (1) the facts must be "reasonably relied upon by experts in the particular field" and (2) the facts must be trustworthy. With such foundations, inadmissible hearsay could support an admissible expert opinion.
New Jersey Zinc Co. v. Cole, 532 S.W.2d 246 (Tenn. 1975), allows a treating doctor to base an opinion on reports of other professionals.
If the bases of expert testimony are not independently admissible, the trial judge should either prohibit the jury from hearing the foundation testimony or should deliver a cautionary instruction. Unfairly prejudicial facts or data should be dealt with under Rule 403. With respect to cross-examination, see Rule 705.
Advisory Commission Comments [2009].
The third sentence is new. Normally a jury should not be allowed to hear the reliable but inadmissible bases underlying an expert's opinion.