Most American courts' rules of evidence prohibit the presentation of hearsay—second-hand statements by people who are not witnesses in a case.
As an exception, however, most jurisdictions allow expert witnesses (including, often, forensic psychiatrists) to rely on hearsay in forming an opinion, so long as the information is typically relied upon by similar experts in their field to form opinions. For example, the Federal Rules of Evidence, Rule 703 specifies:
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. But if the facts or data would otherwise be inadmissible, the proponent of the opinion may disclose them to the jury only if their probative value in helping the jury evaluate the opinion substantially outweighs their prejudicial effect.
When forming an opinion on an evaluee, a forensic psychiatrist often relies in part on information from sources other than the evaluee herself. This collateral information, which may consist of statements from family, friends, co-workers, and others, would ordinarily be classified as hearsay. Certainly, however, collateral information—collection of which is universally considered to be necessary to the practice of psychiatry—would qualify for the exception provided by Rule 703.
These rules may soon be changing. Recently, the California Supreme Court has limited the use of experts disclosing hearsay when explaining an opinion. In People v. Sanchez (63 Cal. 4th 665, 2016), the court held that case-specific statements made by an expert are subject to the same hearsay rules as other testimony. Previously, courts allowed experts to base opinions on hearsay evidence, as long as the information used was typically relied on by experts in the field making a similar evaluation. The court could also inform the jury that they should not consider the hearsay facts forming the expert’s opinion for their truth. However, the Sanchez court opined that:
When any expert relates to the jury case-specific out-of-court statements, and treats the content of those statements as true and accurate to support the expert’s opinion, the statements are hearsay. It cannot logically be maintained that the statements are not being admitted for their truth.
The court pointed out several issues they found concerning including testimonial hearsay. For one thing, if an expert relies on quotes from someone who is not otherwise a witness, there is no chance for opposing counsel to confront the witness or rebut the validity of the statements, a right guaranteed to criminal defendants by the Sixth Amendment.
While ultimately the court decides which evidence is or isn’t allowed, an expert can take steps to avoid forming an opinion based on hearsay. A prepared psychiatric evaluator can specifically ask an evaluee questions, the answers to which would then constitute first-hand knowledge. For example, while a family report saying someone does not take medications may be considered hearsay, asking the evaluee directly about medication usage would not. If an evaluee is unable or unwilling to provide first-hand accounts of important details, an expert can work with a retaining attorney to admit the evidence necessary to form an opinion. For example, a psychiatric expert often relies on past medical records; admitting these records would limit challenges of the expert.
The Sanchez rule applies only to California courts. But its enactment may well influence similar changes in other jurisdictions in the near future.