Faegre Drinker Biddle & Reath LLP, a Delaware limited liability partnership | This website contains attorney advertising.
June 20, 2024

Supreme Court Decides Diaz v. United States

On June 20, 2024, the U.S. Supreme Court decided Diaz v. United States, No. 23-14, holding an expert’s opinion that “most people” in the defendant’s situation have a particular mental state is not an inadmissible opinion “about whether the defendant did or did not have a mental state” under Federal Rule of Evidence 704(b).

When Delilah Diaz tried to drive into the United States from Mexico, an officer stopped the car and found 54 pounds of methamphetamine hidden inside secret compartments. The federal government charged Diaz with “knowingly” importing methamphetamine. Diaz maintained that the car belonged to her boyfriend and that she didn’t know about the drugs. As the case proceeded to trial, the government offered expert testimony that “most” drug couriers are aware that they are carrying drugs. Diaz argued that this expert evidence was inadmissible under Federal Rule of Evidence 704(b), which states that “[i]n a criminal case, an expert witness must not state an opinion about whether the defendant did or did not have a mental state or condition that constitutes an element of the crime charged or of a defense.”

A federal district court ruled the evidence admissible. The government presented its expert testimony at trial, and Diaz was convicted. The Ninth Circuit affirmed.

The Supreme Court affirmed, ruling that an “expert’s conclusion that ‘most people’ in a group have a particular mental state is not an opinion about “the defendant” and thus does not violate Rule 704(b).’” The Court explained that the government’s expert did not testify that “Diaz herself knowingly transported methamphetamine.” His testimony left it to the jury to decide whether Diaz was like the majority of couriers, who know that they are transporting drugs, or not. The Court declined to adopt Diaz’s argument that the expert “functionally” gave an opinion about her mental state. That would only be true, the Court said, if the government’s expert testified that “all” couriers know they are transporting drugs.”

Justice Thomas delivered the opinion of the Court, in which Chief Justice Roberts, and Justices Alito, Kavanaugh, Barrett, and Jackson joined in full. Justice Jackson filed a concurring opinion. Justice Gorsuch filed a dissenting opinion, in which Justices Sotomayor and Kagan joined.

Download Opinion of the Court

The material contained in this communication is informational, general in nature and does not constitute legal advice. The material contained in this communication should not be relied upon or used without consulting a lawyer to consider your specific circumstances. This communication was published on the date specified and may not include any changes in the topics, laws, rules or regulations covered. Receipt of this communication does not establish an attorney-client relationship. In some jurisdictions, this communication may be considered attorney advertising.

Related Topics

The Faegre Drinker Biddle & Reath LLP website uses cookies to make your browsing experience as useful as possible. In order to have the full site experience, keep cookies enabled on your web browser. By browsing our site with cookies enabled, you are agreeing to their use. Review Faegre Drinker Biddle & Reath LLP's cookies information for more details.