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SCOTUS won’t restrict expert testimony in drug trafficking case

Testimony that "most" drug mules know what they are carrying was admissible because it didn't refer specifically to the defendant's state of mind, the justices found in a split decision.

WASHINGTON (CN) — The Supreme Court on Thursday refused to draw new lines around the kind of expert testimony the government can present in a drug trafficking case.

In a 6-3 ruling, the court upheld the government’s use of expert testimony about the mental state of most drug couriers, in the case of a woman convicted of knowingly transporting methamphetamine across the U.S.-Mexico border.

“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),” Justice Clarence Thomas wrote for the majority. 

Federal law prohibits expert witnesses from sharing opinions on a defendant’s mental state in criminal cases. The George H.W. Bush appointee said this logic prevents witnesses from taking over the jury’s role. 

Leading the dissent, Justice Neil Gorsuch said the court had carved a path around the rule against offering opinions on a defendant’s guilt. The Donald Trump appointee said his colleagues gave the government a powerful new tool. 

“Prosecutors can now put an expert on the stand — someone who apparently has the convenient ability to read minds — and let him hold forth on what ‘most’ people like the defendant think when they commit a legally proscribed act,” Gorsuch wrote. 

Deliah Diaz brought a challenge to expert testimony used against her after she was caught transporting $370,000 worth of methamphetamine across the border. Diaz was driving back to California after a trip to Mexico when she was stopped at the San Ysidro border crossing. An officer asked her to roll down her car’s rear windows, but Diaz claimed she was unable to because the windows were manual.

The border patrol officer later found packages of methamphetamine stuffed inside the window compartment, making it impossible to roll down the window.

Diaz claimed she didn’t know the drugs were in the car because she was borrowing the vehicle from her boyfriend. A jury still found Diaz guilty of knowingly importing methamphetamine because a government expert testified that drug traffickers do not typically entrust drugs to an unknowing person. The justices' ruling means her conviction and seven-year sentence are upheld.

The government defended the expert’s testimony at the Supreme Court in March, arguing that the testimony didn’t offer an opinion on Diaz’s mental state. Instead, Matthew Guarnieri, assistant to the solicitor general at the Justice Department, said the expert testified that most drug mules know what they are carrying.

Diaz claimed that expertise implied information to the jury about her state of mind.

The court disagreed, noting that the expert testified about the mental state of most drug couriers, not Diaz specifically.

“Because Agent Flood did not express an opinion about whether Diaz herself knowingly transported methamphetamine, his testimony did not violate Rule 704(b),” Thomas wrote about the witness. 

Thomas said Diaz could present evidence to differentiate herself from other drug couriers, and he noted she did so during the trial. 

“The jury was thus well aware that unknowing couriers exist and that there was evidence to suggest Diaz could be one of them,” Thomas wrote. “It simply concluded that the evidence as a whole pointed to a different conclusion: that Diaz knowingly transported the drugs.” 

Thomas said expert testimony about an entire group would be prohibited, but in Diaz’s case the expert said she was part of a group that may or may not have a particular mental state. 

“Of all drug couriers — a group that includes Diaz — he opined that the majority knowingly transport drugs,” Thomas wrote. “The jury was then left to decide: Is Diaz like the majority of couriers?” 

Justice Samuel Alito said in March that there are already rules prohibiting testimony claiming 100% of drug mules knew what they were carrying. Alito said it was unnecessary for the court to draw new lines on this topic. 

“There are other rules that take care of the extreme cases,” Alito, a George W. Bush nominee, said at arguments. 

Justice Ketanji Brown Jackson wrote a concurring opinion, noting that the rule is not party agnostic. While neither the government or defense can call an expert to offer their opinion on a defendant’s guilt, the Joe Biden appointee said both sides are permitted to use expert testimony on the likelihood that the defendant had a particular mental state. 

Diaz, Jackson noted, called an automobile specialist who testified that a driver of her car would almost certainly not know that it contained drugs. 

“Far from disserving our criminal justice system, the type of mental-state evidence that Rule 704(b) permits can be of critical assistance to lay factfinders tasked with determining a defendant’s mental state as an element of the alleged crime (or defense),” Jackson wrote. 

Justices Sonia Sotomayor and Elena Kagan, both Barack Obama appointees, joined Gorsuch’s dissent, which said that speculative guesswork about the defendant’s state of mind undermines the seriousness due to criminal proceedings. 

“It diminishes our respect for the presumptively free person, his free will and individuality, by encouraging the lazy assumption that he thinks like ‘most,’” Gorsuch wrote. “And it reduces the vital role juries are meant to play in criminal trials.” 

Follow @KelseyReichmann
Categories / Appeals, Courts, Criminal

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