Former President Donald Trump has made combating the influx of drugs across America's southern border a key part of his platform.

This week saw the Supreme Court hand down a decision that will make Trump's battle easier to wage. 

Case concerned use of expert testimony regarding drug traffickers

According to Breitbart, America's highest judicial body ruled on Thursday to uphold the conviction of Delilah Diaz, who was caught with 54 pounds of methamphetamine as she attempted to cross over from Mexico.

Diaz denied knowing that the narcotics were in her vehicle, an element which federal prosecutors had to prove in order to convict her of importing drugs.

Common Clarence Thomas W https://t.co/D4raFJirQk

— Breitbart News (@BreitbartNews) June 21, 2024

Homeland Security Investigations (HSI) Special Agent Andrew Flood appeared at her trial as an expert witness and testified that drug traffickers do not typically place such large quantities of drugs in vehicles belonging to unwitting travelers.

Diaz challenged the validity of Flood's testimony under the federal rules of evidence, arguing that he was offering an inadmissible opinion about her mental state or condition.

Agent "did not express an opinion" on defendant's mental state

Yet in a six to three decision, justices determined that Flood's remarks did not amount to an opinion and could thus be admitted at trial.

"In this case, Agent Flood did not express an opinion about whether Diaz herself knowingly transported methamphetamine," Justice Clarence Thomas said in writing for the majority.

"Instead, he testified about the knowledge of most drug couriers. That opinion does not necessarily describe Diaz's mental state," Thomas continued.

"Because Agent Flood did not express an opinion about whether Diaz herself knowingly transported methamphetamine, his testimony did not violate Rule 704(b)," the justice declared.

"An opinion about most couriers is not an opinion about all couriers"

Thomas went on to declare that "Diaz’s counter arguments are unpersuasive" as "an opinion about most couriers is not an opinion about all couriers."

"Agent Flood asserted that Diaz was part of a group of persons that may or may not have a particular mental state. The ultimate issue of Diaz's mental state was thus left to the jury’s judgment," Thomas went on to add.

Thomas was joined in his opinion by Chief Justice John Roberts along with Justices Samuel Alito, Brett Kavanaugh, Amy Coney Barrett, and Ketanji Brown Jackson. Meanwhile, Justices Neil Gorsuch Sonia Sotomayor and Elena Kagan responded with a dissent.