The US Supreme Court has agreed to examine the evidentiary scope of expert witness testimony for demonstrating intent in a drug trafficking case, known as Diaz v. United States. This follows a petition for reconsideration brought forward by Delilah Diaz, a California resident convicted of bringing drugs into the US. The conviction was sustained through expert testimony disputing Diaz’s assertion that she wasn’t aware she was carrying drugs.
The case seeks to address the issue of scope in expert witness testimony, with the key focus being Federal Rule of Evidence 704(b), which has been a subject of discordance in past circuit courts. The application and interpretation of this rule have resulted in conflicted court rulings. The Ninth Circuit, Eighth Circuit, and Eleventh Circuit have all approved of the proceedings. On the other hand, the Fifth Circuit has consistently found that the directive disallows both direct and implied opinions on the defendant’s awareness.
In Diaz’s appeal, it is implicated that the stance of the Ninth Circuit is erroneous. Based on her petition, the allegation is that the Ninth Circuit’s interpretation of Rule 704(b) violates the rule’s text, which prohibits conclusive opinions about a defendant’s mental condition, not just explicit ones. This presumption purportedly lightens the Government’s obligation to establish understanding beyond a reasonable doubt, as it allows generalization about a particular defendant group rather than focusing on evidence specific to the actual defendant.
Diaz concludes by arguing that allowing such forms of expert witness testimony infringes upon “elementary notions of due process.” The Supreme Court is anticipated to begin oral hearings on the subject next year.