When Is Hearsay Admissible in Expert Witness Testimony?

The rules of hearsay have long been a stumbling block for attorneys who rely on oral testimony and documentary evidence. In the past, we were able to rely on expert witness testimony to present otherwise inadmissible hearsay evidence, but three landmark Supreme Court cases have reshaped the rules for hearsay as it relates to expert testimony in court: People v. Sanchez, People v. Perez, and People v. Leon. People v. Sanchez has been especially impactful.

Case #1: People v. Sanchez

When the California Supreme Court issued People v. Sanchez (2016) 63 Cal.4th 665, the court severely limited the use of hearsay by prosecution experts. Sanchez involved a police gang “expert” who testified to various hearsay statements in support of street gang allegations.

The court ruled:

If an expert testifies to case specific out of court statements to explain the bases for his opinion, those statements are necessarily considered by the jury for their truth, thus rendering them hearsay. Like any other hearsay evidence, it must be properly admitted through an applicable hearsay exception. (Id. at p. 684; fn. omitted.)

The court clarified:

What an expert cannot do is relate as true case specific facts asserted in hearsay statements, unless they are independently proven by competent evidence or are covered by a hearsay exception. (Id. at p. 686; emphasis in original.)

The court ultimately ruled that “the case-specific statements related by the prosecution expert concerning defendant’s gang membership constituted inadmissible hearsay” because “they were recited by the expert, who presented them as true statements of fact, without the requisite independent proof.” (Id. at p. 670.)

The barring of prosecution hearsay has been in effect since the case of Crawford v. Washington (2004)—but the defense was largely unaffected by this ruling. The United States Supreme Court has stated that “because hearsay statements of this sort are, by definition, offered by the accused, the admission of such statements does not implicate Confrontation Clause concerns.” (Lilly v. Virginia (1999) 527 U.S. 116, 130.)

In Giles v. California, Justice Antonin Scalia further clarifies that Crawford never applies against the defense. The asymmetrical nature of the Constitution’s criminal trial guarantees is not an anomaly, but the intentional conferring of privileges designed to prevent criminal conviction of the innocent. The State is at no risk of that. (Giles v. California (2008) 554 US. 353, 376, fn. 7.)

But the Sanchez case took things a step further, revising the rules in a way that significantly impacts not just the prosecution but any expert witness testimony. In order to understand the specific rule, we have to consider rulings from the three cases mentioned in the opening paragraph above.

The first is Sanchez itself: Any expert testimony in court may still rely on hearsay in forming an opinion, and the jury may be notified of such in general terms.

Because the jury must independently evaluate the probative value of an expert witness testimony, Evidence Code section 802 properly allows an expert to relate generally the kind and source of the “matter” upon which his opinion rests. A jury may repose greater confidence in an expert who relies upon well-established scientific principles. It may accord less weight to the views of an expert who relies on a single article from an obscure journal or on a lone experiment whose results cannot be replicated. This is important to bear in mind when qualifying an expert witness.

There is a distinction to be made between allowing an expert to describe the type or source of the matter relied upon as opposed to presenting, as fact, case-specific hearsay that does not otherwise fall under a statutory exception. What an expert cannot do is relate as true case-specific facts asserted in hearsay statements, unless they are independently proven by competent evidence or are covered by a hearsay exception.

Simply notifying the jury of hearsay evidence in general terms may do less to bolster the weight of the opinion. It can, however, accomplish the following:

• First, the argument confirms that the proffered case-specific hearsay assertions are being offered for their truth. The expert is essentially telling the jury, “You should accept my opinion because it is reliable in light of these facts on which I rely.”
• Second, in a criminal prosecution, while Crawford and its progeny may complicate some heretofore accepted evidentiary rules, they do so under the compulsion of a constitutional mandate as established by binding Supreme Court precedent. (People v. Sanchez, supra, 63 Cal.4th 665, 685-686.)

Case #2: People v. Perez

Next is People v. Perez (2017) 4 Cal.5th 421, 456 (Emphasis ORIGINAL): If an expert witness testimony relies on case-specific out-of-court statements on which he or she relied for their truth to form an opinion, such statements are also “necessarily considered by the jury for their truth, thus rendering them hearsay.” (Sanchez, supra, 63 Cal.4th at p. 684.)

But an expert witness testimony may nonetheless “rely on hearsay in forming an opinion, and may tell the jury in general terms that he did so “without violating hearsay rules or the confrontation clause.” (Id. at p. 685; see also People v. Leon (2015) 61 Cal.4th 569, 603 [“It is also clear that testimony relating the testifying expert’s own, independently conceived opinion is not objectionable, even if that opinion is based on inadmissible hearsay.”].)

Case #3: People v. Leon

The third case is People v. Leon (2015) 61 Cal.4th 569, 603: It is also clear that testimony relating the testifying expert’s own, independently conceived opinion is not objectionable, even if that opinion is based on inadmissible hearsay. (Evid. Code, § 801, subd. (b); People v. Montiel (1993) 5 Cal.4th 877, 918 [21 Cal.Rptr.2d 705, 855 P.2d 1277].)

During an expert testimony in court, the testifying expert can be cross-examined about these opinions. The hearsay problem arises when an expert simply recites portions of a report prepared by someone else, or when such a report is itself admitted into evidence. In that case, out-of-court statements in the report are being offered for their truth.

Admission of this hearsay violates the confrontation clause if the report was created with sufficient formality and with the primary purpose of supporting a criminal prosecution.

The Rules for Hearsay in Expert Witness Testimony

So here’s what we can conclude from these three cases:

• Your expert can testify on direct that he or she relied on hearsay in forming an opinion.
• Your expert may, in support of that opinion, tell the jury in general terms that he or she relied on this hearsay.
• Your expert is permitted to “generally describe” the hearsay. (People v. Sanchez, supra, 63 Cal.4th 665, 686.)

This doesn’t get us as far as we need, which is to get the expert to describe the hearsay in detail. But we need to push the envelope on this point. When qualifying an expert witness, prepare them to testify that hearsay from various sources was the basis for the expert’s opinion. Have the expert describe those sources in as much detail as he or she can and the court permits.

Of course, if we can lure the prosecutor into asking for details, we can prime the expert to unload as much hearsay as possible in support of the expert’s opinion.