Supreme Court upholds conviction of California woman in drug case

The California woman argued she unknowingly was transporting drugs for her boyfriend.

The Supreme Court upheld the conviction of a California woman who claimed she was unaware of methamphetamine hidden in her car, despite arguments regarding expert testimony.

The majority opinion of 6-3 dismissed claims that the prosecution’s expert witness overstepped by suggesting the woman’s awareness based on common behavior among drug couriers.


The big picture: Justice Clarence Thomas wrote the majority decision, emphasizing that an opinion about most couriers did not apply to all couriers.

  • Justice Neil Gorsuch dissented strongly, warning that the ruling could become a powerful tool for the government by allowing experts to speculate on defendants’ mental states.

Driving the news: Delilah Guadalupe Diaz, sentenced to seven years for drug charges, argued that she was unknowingly transporting drugs for her boyfriend, labeling herself as a “blind mule” used by cartels.

  • The prosecution’s expert witness, a Homeland Security agent, testified that cartels typically do not send drugs with individuals unaware of the contraband, influencing the case against Diaz.
  • Diaz appealed her conviction on the grounds of the expert witness breaching the rule that prohibits experts from opining on a defendant’s mental state, revealing a split among lower courts on the issue.
  • The regulation against expert opinions on a defendant’s mental state originated from the trial of John Hinckley Jr. in 1981, who was found not guilty by reason of insanity for the shooting of President Ronald Reagan.
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