The Expert's Examiner


EXPERT OPINIONS-THE SUPREME COURT HANDS DOWN TWO RULINGS THAT DIRECTLY AFFECT EXPERT TESTIMONY
January 2, 2025

by Charles Bennett

The Supreme Court handed down several criminal procedure cases in the 2023-2024 term. Since June 2024 when the cases were decided, Supreme Court practitioners have commented that two of the cases have relevance to attorneys and expert witnesses involved in corporate defense.

Smith v. Arizona, 144 S. Ct. 1785, 602 U.S. 779 (2024).  On June 20, 2024, The Supreme Court handed down a decision which turned on the question of the federal constitutional right to confront the witnesses against them and bars the “testimonial statements” of an absent expert witness except in circumstances where they are unavailable to testify, and the defendant has had an opportunity to cross-examine.  The case involved the arrest of the defendant Smith on drug and distribution charges and the evidence was gathered by law enforcement at the scene and sent to the AZ state crime lab where a lab analyst ran tests, generated notes based on observation and signed a report. However, at trial the prosecution decided to put another analyst (“a substitute expert”) who relied on the original analyst’s report to confirm his opinions related to the type and amount of drugs found in defendant Smith possession.

The Supreme Court was asked to decide how the Confrontation Clause affects testimony when an expert witness uses the factual assertation of an absent lab analysis to support their own opinions while on the witness stand.  The Court confirmed that Smith had the right to cross-examine the first lab analyst (“i.e., forensic expert”) stating the defense has the right to confront the expert that provided the report based on the firsthand knowledge developed from tests and observations and the prosecution may not substitute another expert when that testimony is tantamount to hearsay.

Going forward experts and trial practitioners should be mindful of the broad reach of Smith v. Arizona.  The holding applies broadly to any type of forensic testing, including for example the work of forensic accountants and other similarly situated experts that are asked to testify based on another expert’s work.

Diaz v. United States, 144 S. Ct. 1727, 602 U.S.  (2024).  Like Smith, the criminal acts in this matter involved the arrest by the border patrol of Diaz and the discovery of more than 50 pounds of methamphetamines in the vehicle Diaz was using to enter the country.  Defendant Diaz denied knowing that the drugs were in the vehicle when she was arrested and thus, she did not knowingly attempt to transport drugs into the US.

At trial the prosecution gave notice that they were calling an expert and the proffer indicated that the expert would testify about the common practices of Mexican drug-trafficking cartels and the distrust they have of sending large quantities of drugs to people who were unaware they are transporting them. 

The defense objected relying on FRE 704(b) which provides that an expert witness in a criminal case cannot opine on the defendant’s state of mind since that constitutes an element of the crime(s) charged.  In other words, the rules of evidence bar an expert witness from infringing on the role of the jury by stating their opinions or conclusions about whether a defendant has the requisite mental state to satisfy an element of the crime. 

The prosecution defended the testimony relating to the general state of mind that “group” might have, stating that Rule 704(b) does not prohibit testimony about the defendant’s mental state.

The Supreme Court confirmed a narrow exception to Rule 704(b) that permits an expert to provide opinions about the general mental state of a “group” of actors such as drug distributors, while reiterating the prohibition of testimony that includes an opinion or conclusion on the precise elements of the underlying crime.

The holding in Diaz applies to any crime that turns on a defendant’s state of mind and thus all trial counsel should be wary of its impact in cases involving a defendant’s mental state.