Supreme Court wrestles with dispute over expert testimony in drug 'mule' case

WASHINGTON — When thousands of dollars' worth of pure methamphetamine was found in a car driven by Delilah Guadalupe Diaz, she claimed she didn't know about the illegal cargo.

Diaz's argument at trial failed, but her legal fight continued, with the Supreme Court on Tuesday considering whether prosecutors could submit evidence inferring that people convicted of being drug mules generally know what they are transporting.

Diaz was sentenced to seven years in prison and is appealing her drug trafficking conviction.

A U.S. citizen living in California, Diaz was stopped by a Border Patrol agent in August 2020 after crossing into the United States from Mexico at the San Ysidro port of entry.

She told the agent the car was her boyfriend's. The agent then asked her to roll down the rear window. She said it was manual, and the officer tried to open it himself. According to the Justice Department, the agent encountered resistance and heard a crunching sound, which can be a sign that drugs have been hidden inside the vehicle.

A search revealed 55 pounds methamphetamine with a retail value of $368,550.

Diaz has maintained that she did not know the drugs were in the car, saying her boyfriend had loaned it to her when she was returning to the U.S. from a trip to Mexico.

At issue at the Supreme Court is a rule of evidence that was amended after John Hinckley Jr. was found not guilty based on his insanity defense for the attempted assassination of President Ronald Reagan in 1981. Congress amended the rule in an effort to exclude testimony by expert witnesses about a defendant's mental state

The rule says "an expert witness must not state an opinion about whether the defendant did or did not have a mental state or condition that