The Supreme Court on Thursday upheld a California woman’s drug smuggling conviction, based on expert testimony that found criminal organizations rarely use “blind couriers” to move drugs across the southern border.
In a 6-3 decision, the justices rejected Delilah Diaz’s argument that the expert testimony was unfair and illegal because it strongly suggested to the jury that she must have known there were drugs in the car.
Federal rules of evidence say experts cannot comment on a defendant’s “mental state or condition,” but the justices said the expert’s testimony about drug trafficking operations in general did not violate those rules.
Liberal Justice Ketanji Brown Jackson, who joined most of the Supreme Court’s conservatives in deciding Diaz v. United States, said experts often testify on both sides of a case.
“This case illustrates how important mental state evidence can be to both parties in a criminal trial,” Judge Jackson wrote in his concurring opinion. “The government’s expert (based on his nearly 30 years of experience as a special agent) opined that ‘in most cases’ drug mules know they are transporting drugs. … Notably, however, the government was not the only one to rely on this type of mental state evidence during trial. Judge Diaz called an automobile expert, who testified that the driver of her vehicle would most likely not know that there were drugs in it.”
Diaz, a US citizen, was stopped at a border crossing while returning from Mexico in August 2020. A Border Patrol agent asked her to roll down one of her car windows, to which she replied it was manual. When he tried, he heard a “crunching noise coming from the door,” she said.
After pulling the vehicle over and searching it, officers found 56 packets of methamphetamine hidden inside the door panels and under the carpet in the trunk, weighing just over 54 pounds with an estimated retail value of $368,550.
Diaz said the car belonged to her boyfriend and she didn’t know anything about drugs.
She was charged with drug trafficking, and prosecutors needed to prove to the jury that she knew she was transporting drugs.
They called in Special Agent Andrew Flood of the Department of Homeland Security, who testified that in his experience, drug traffickers “do not typically entrust large quantities of drugs to people who do not know they are carrying drugs.”
Diaz was convicted and sentenced to seven years in prison. A San Diego federal judge and the Ninth Circuit Court of Appeals rejected her arguments that the deputies’ testimony violated federal law.
The Supreme Court agreed to hear her appeal but upheld her conviction on Thursday.
“Because Agent Flood did not express an opinion as to whether Diaz himself knowingly transported methamphetamine, his testimony did not violate the federal rules,” Justice Clarence Thomas wrote in the majority opinion. “An expert’s conclusion that ‘most people’ in a group have a particular mental condition is not an opinion about the defendant.”
Chief Justice John G. Roberts Jr., Justice Samuel A. Alito Jr., Justice Brett M. Kavanaugh, Justice Amy Coney Barrett and Justice Jackson concurred.
In his dissent, conservative Justice Neil M. Gorsuch wrote, “The government has gained a powerful new tool: prosecutors can call on the stand an expert who apparently has the convenient ability to read minds and who can tell them what “most” people like the defendant are thinking when they commit legally prohibited acts. … No one knows what basis there is for permitting such a travesty in a federal criminal trial, but it is certainly not found in the Federal Rules of Evidence.”
Justices Sonia Sotomayor and Elena Kagan joined Gorsuch’s opinion.
San Francisco attorney Hilary Irvin, a former federal prosecutor, said the ruling “marks a dark day for criminal defendants.”
“They rely on the gatekeeping function of the courts and the law to exclude evidence that would almost certainly result in a ruling in the government’s favor.”
But “the reality is that juries rely on expert testimony to make important judgments about a defendant’s conduct,” Ervin continued. “Currently, the government can present witnesses to lead the jury directly to a government verdict.”
