Thomson Reuters Attorney Analysis
Diaz and 704 ( b )
Applying this framework to the Diaz facts , the Court held that the exception found in Rule 704 ( b ) did not preclude the expert testimony at issue because it concerned the state of mind of drug-couriers as a group , rather than the state of the mind of the individual defendant .
In other words , the Court made a distinction between expert testimony that most drug-couriers know they are transporting drugs and expert testimony that all drug-couriers know they are transporting drugs , which necessarily includes Diaz despite not mentioning her by name .
Writing for the dissent , Justice Neil Gorsuch makes a compelling case for a much broader interpretation of the exception than that adopted by the majority .
According to the dissent , because the plain language of Rule 704 ( b ) bars opinions “ about ” whether the defendant had a particular mental state , it should encapsulate any expert opinions on the subject of mens rea , including those that are probabilistic (” most ”) rather than conclusory (” all ” or “ none ”). Any other interpretation is neither necessary nor appropriate under the text of 704 ( b ), which explicitly states that “ matters ” of mens rea “ are for the trier of fact alone .”
Opening for expert witnesses
In her concurring opinion , Justice Kentanji Brown Jackson points out that the prohibitions of Rule 704 ( b ) apply equally to the
Government and the defense . So although the rule worked against Diaz in this case , defendants in future cases may call their own expert witnesses to testify that they likely did not have the requisite mental state based on their membership in a particular group .
While the majority holding is generally consistent with the purpose of Rule 704 in that it leaves the ultimate issue of whether the defendant shared the state of mind of “ most ” similarly situated individuals to the jury , it is likely to greatly expand the use of expert testimony concerning the defendant ’ s state of mind by both parties in criminal cases .
There is also legitimate concern , raised in both the concurrence and the dissent , that jurors give disproportionate weight to the testimony of law enforcement agents frequently testifying as experts for the prosecution , as opposed to those experts called by the defense .
Bias , reliance and expert witnesses
Defense attorneys should be mindful of this bias in selecting expert witnesses and consider other tools at their disposal to combat the government ’ s increased reliance on expert testimony to prove mens rea . Defense attorneys may look to Justice Gorsuch ’ s dissent .
The Justice writes that defense attorneys may employ other Federal Rules of Evidence to exclude expert testimony concerning the defendant ’ s mental state that is either irrelevant ( Rule 402 ) or prejudicial ( Rule 403 ), despite that the evidence is otherwise not precluded under the Court ’ s narrow reading of Rule 704 ( b ).
About the authors
Nicole Boeckmann ( L ), a former division chief at the Eastern District of New York , is a partner in the Bracewell government investigations and enforcement practice . She can be reached at nicole . boeckmann @ bracewell . com . Meagan Maloney ( R ) is an associate in the firm ’ s Austin office and focuses on white collar criminal defense , government investigations and regulatory compliance .
This article was first published on Reuters Legal News and Westlaw Today on July 10 , 2024 .
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