Diaz v. United States

Brief of Amicus Curiae National Association of Criminal Defense Lawyers in Support of Petitioner

Brief filed: 01/03/2024

Documents

Diaz v. United States

United States Supreme Court; Case No. 23-14

Argument(s)

This case turns on the interpretation of Federal Rule of Evidence 704(b). Specifically, the Court must decide whether that rule allows a law enforcement officer—functioning as an expert witness in a drug trafficking case—to testify that most defendants caught with drugs at the border know that they are transporting drugs. The answer to this question is “no”: law enforcement officers cannot properly testify as experts about the mens rea of similarly situated defendants as a class. That conclusion follows from the plain text of Rule 704(b), as Petitioner explains. Simply put, Rule 704(b) forbids any expert opinion “about whether” a defendant has a mental state; expert testimony about classwide mens rea unquestionably concerns the mens rea of the defendant and is therefore prohibited by the Rule.

Author(s)

Sean Hecker, David Patton, and Sean Kelly, Kaplan Hecker & Fink LLP, New York, NY; Joshua L. Dratel, Law Offices Of Dratel & Lewis, New York, NY; Carmen Iguina González and Joshua Matz, Kaplan Hecker & Fink LLP, Washington, DC

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