Diaz v. United States
View Official PDFSummary
A short, plain-English overview of Diaz v. United States.
In Diaz v. United States, the Supreme Court addressed whether expert testimony regarding the mental state of most drug couriers violated Federal Rule of Evidence 704(b). The Court affirmed the lower court's decision, concluding that the testimony did not explicitly state an opinion about Diaz's mental state. The testimony was deemed permissible as it did not directly address whether Diaz knowingly transported methamphetamine.
Holding
The single most important “bottom line” of what the Court decided in Diaz v. United States.
The Court held that expert testimony about the mental state of 'most people' in a group does not violate Rule 704(b) as it does not directly address the defendant's mental state.
Key Quotes
Short excerpts from the syllabus in Diaz v. United States that support the summary and concepts above.
Expert testimony that 'most people' in a group have a particular mental state is not an opinion about 'the defendant.'
Agent Flood did not express an opinion about whether Diaz herself knowingly transported methamphetamine.
An opinion about most couriers is not an opinion about all couriers.
