CALIFORNIA EVIDENCE UPDATE 2024

Written by Chris Chambers Goodman^*

UNITED STATES SUPREME COURT OPINIONS ON EXPERTS AND THE CONFRONTATION CLAUSE

The United States Supreme Court issued two evidence opinions in 2024! The first, Diaz v. Arizona,¹ held that expert testimony that most people have a particular to mental state when carrying drugs was not a specific opinion about the particular defendant’s mental state, and therefore did not violate Federal Rule of Evidence 704(b).² The expert witness, testifying about drug couriers, stated that "in most circumstances, the driver knows they’re hired . . . to take the drugs from point A to point B" because using someone who did not know they were carrying drugs "would expose the drug-trafficking organization to substantial risk."³ Justice Thomas’s majority opinion reasoned that this testimony was not an opinion about whether that particular defendant knowingly transporting drugs.⁴ Therefore, the court concluded that the language 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)."⁵

The next day, the Court announced the opinion in Smith v. Arizona,⁶ recognizing the "muddle" of confusion that has emerged from the court’s confrontation clause jurisprudence.⁷ The petitioner challenged testimony by a representative of the Department of Public Safety regarding testing drugs that were found on his person. One analyst ran the tests and signed a report about the testing.⁸ The state substituted a different analyst as the testifying expert and claimed that he would provide "an independent opinion on the drug testing performed by" the first analyst, who no longer worked at the department.⁹ The testifying analyst referred to testing the first analyst had done, to her notes, and even told the jury what her records conveyed. He then gave his opinion that the various items seized "contained usable quantities" of particular controlled substances (which is what the first analyst had also concluded).¹⁰ The testifying expert testified that he was making his "own independent opinions,"¹¹ and the Court considered the question of whether his opinion was nevertheless based on case-specific hearsay and violated the confrontation clause. Deciding that it was indeed case-specific hearsay, the Court explained that the state used the testifying expert "to relay what . . . [the non-testifying analyst] wrote down about how she identified the substances" and "effectively became [the non-testifying analyst’s] . . . mouthpiece."¹² The Court remanded to the trial court