Blind Mules

In a 6-3 ruling with a nearly ideologically divided Court, SCOTUS ruled in Diaz v. United States that Rule 704(b) of the Federal Rules of Evidence does not prohibit an expert witness from testifying that “most” people who are caught transporting drugs know that they are in fact transporting drugs. This kind of expert testimony is used to counter the so-called blind mule defense. The ruling is important because before a person can be convicted of transporting drugs the government must prove that the person knows that they are transporting drugs.

Rule 704(b), FRE

Federal Rule of Evidence 704(b) says: “In a criminal case, an expert witness must not state an opinion about whether the defendant did or did not have a mental state or condition that constitutes an element of the crime charged or of a defense. Those matters are for the trier of fact alone.” In nearly every criminal case, one of the elements of the crime is that the defendant have some specified mental state (mens rea if you want to be fancy about it). The mental state might be purposefully, knowingly, recklessly, or negligently, depending on the crime, but there is almost always some mental state that the government must prove.

Mental state is frequently the most hotly disputed issue in a criminal case. And since many defendants do not confess to their mental state, prosecutors are left pointing to circumstantial evidence from which a jury can infer what was in the defendant’s mind at the time he committed the crime.

Rule 704(b) was adopted by Congress in 1981 in response to the not guilty by reason of insanity verdict of John Hinckley for attempting to assassinate President Reagan. Hinckley’s trial included conflicting testimony from various expert witness who opined on Hinckley’s mental state.

Case Background

Diaz was driving a car from Mexico into the United States when she was stopped by Boarder Patrol who found 54 pounds of meth hidden in the doors of the car. Diaz told them she had no idea the drugs were there. To combat Diaz’s blind mule defense, the government called a Homeland Security Agent as an “expert” in drug trafficking. The Agent told the jury that “in most circumstances, the driver knows they are hired . . . to take the drugs from point A to point B.” The Agent was not permitted to testify that all mules know they are transporting drugs. He admitted that some mules are in fact blind. Given this admission it’s a little difficult to see what the point of the testimony was other than the hope that the jury would convict Diaz based on the Agent’s testimony that it is more likely for a drug mule to know about the drugs than to be blind.

Majority

Justice Thomas wrote the majority opinion and agreed with the government that Rule 704(b) only prevents the expert from testifying that the specific defendant had the requisite mental state which constitutes an element of the crime. Testimony that the defendant belongs to a class of people of whom most, but not necessarily all, have the requisite mental state does not violate the rule. If an expert testified that all members of a class which the defendant was a part of had the requisite mental state, that would violate the rule. But saying most is perfectly fine.

Justice Thomas reasoned that “Rule 704(b) . . . proscribes only expert opinions in a criminal case that are about a particular person (‘the defendant’) and a particular ultimate issue (whether the defendant has ‘a mental state or condition’ that is ‘an element of the crime charged or a defense”). Because the Agent did not testify that Diaz herself knew drugs were in the car, his testimony was permissible. After all, “Diaz may or may not be like most drug couriers.”

Justice Jackson’s concurrence

I was a little surprised to see that Justice Jackson concurred with the majority given that she is the first public defender to ever ascend to the Supreme Court. 

Justice Jackson wrote separately to emphasize that Rule 704(b) is “party agnostic.” She believes that the Court’s ruling in Diaz will allow defendants to call experts to testify about most people having a particular mental state that constitutes an element of a defense. She specifically pointed to a hypothetical expert testifying that most people who are schizophrenic and commit a crime do so because they don't appreciate the wrongfulness of their conduct, or an expert who testifies about the typical mental state of victims of domestic violence which could prove useful to a defendant in a battered spouse case.

She may be right that there will be instances when the new limitation on Rule 704(b) will prove helpful to the defense, but I suspect the cost will far outweigh the benefits. Time will tell.

Dissent

Justice Gorsuch wrote the dissent which was joined by Justices Sotomayor and Kagan. The dissent rightfully excoriates the majority for narrowing the scope of Rule 704(b) to now allow expert witnesses to testify about the mental state of a defendant—something explicitly prohibited by the rule. So that issue is lost, at least for now. The more important part of the dissent in my view is that it points out several other rules of evidence that can be employed to challenge this kind of testimony.

Justice Gorsuch points to Rules 401, 402, and 403 of the Federal Rules of Evidence which prohibit the introduction of irrelevant evidence, and even relevant evidence if its probative value is substantially outweighed by the danger of unfair prejudice.

He also points out that defendants may mount successful challenges to this kind of expert testimony under Rule 702. That rule allows expert testimony only when “it is more likely than not that: (a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue; (b) the testimony is based on sufficient facts or data; (c) the testimony is the product of reliable principles and methods; and (d) the expert's opinion reflects a reliable application of the principles and methods to the facts of the case.” In the dissent’s view, the kind of drug mule testimony at issue in Diaz cannot meet any of these standards. 

Conclusion

My gut reaction to reading the majority opinion in Diaz was that it was a significant blow to criminal defendants. But in his dissent, Justice Gorsuch laid out a blueprint for defense lawyers to challenge such evidence under other rules going forward. It’s a dissent that every federal criminal defense lawyer in America should read carefully. And then read it again. Because you can rest assured that every prosecutor at the DOJ is reading it.

adam@ruffinappeals.com

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