An opinion piece by Josh Perry

On June 20th the Supreme Court struck down some extra-textual barriers to civil suits for retaliatory arrest and malicious prosecution – while making it much easier for accused people to get wrongfully prosecuted and convicted in the first place. It’s a bad trade-off.

Everyone agrees that Delilah Diaz drove across the U.S.-Mexico border with 54 pounds of methamphetamines. The only question in her federal prosecution was whether she “knowingly” transported the drugs. She said she was a blind courier, ignorant of her cargo. So, at trial, the government bolstered its mens rea argument by calling a homeland security investigator to testify that “most people” who cross the border with drugs know that they’re couriers. The jury was convinced; the Fifth Circuit affirmed; and today the Supreme Court did, too, in Diaz v. United States.

Why? Well, Federal Rule of Evidence 704(b) bars an expert witness in a criminal case from opining “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.” And, writing for six justices, Justice Thomas argued that the DHS agent did not testify “about” Diaz’ own mental state, and did not state a definite opinion. He just offered a probabilistic assessment about everyone else in Diaz’s positions. And hey, if the jury draws an inference, that’s on them.

Justice Gorsuch’s dissent, joined by Justices Kagan and Sotomayor, rejected both pieces of the majority’s reasoning. It’s true that the agent didn’t specifically attribute scienter to Diaz herself – but even the strictest textualists consider context. And the only reason the agent’s testimony was relevant at all was the inescapable implication that Diaz, purportedly like other people in her position, knew what she was doing. So if the agent’s opinion wasn’t “about” Diaz, it should have been excluded anyhow. And it did have something to do with Diaz, it fell under the plain meaning of the text.

And, the dissent fumed, the majority was just playing games with probabilities. What if the agent had testified that 95% of people in Diaz’s position know what they’re carrying? 99%? Would that been enough to convince the Court that he was offered an opinion “about” Diaz herself?

Consider: I read a lot of Supreme Court decisions. I’m an appellate lawyer. And it’s my expert opinion that most justices who misread the plain language of criminal evidence rules, and disregard glaringly obvious context, are cynically trying to advantage the prosecution at the expense of defendants by making it easier to lock people up without proof of criminal intent. I’m not saying, of course, that Clarence Thomas did exactly that. I’m just telling you the odds.

The dueling opinions purported, consistent with the justices’ avowed textualist commitments, to debate the meaning of a preposition. But practically, the justices were arguing about whether liberty should hinge on police officers’ untested intuitions about group propensities.

How hard will it be to find a cop who will testify: Most people driving a stolen car know that it’s stolen. (I’ve heard that one.) Most women out after 12 am on a downtown streetcorner intend to sell sex. (Ditto). Most people with $82 in cash and five zips intend to distribute, not simply possess, the drugs. (Ditto, a hundred times). Most people who discharge a gun intend to commit serious bodily injury. (Yup.) And on and on.

The problem is that the jury is supposed to infer these things from the evidence – not take it as gospel from a police officer who launders his obviously biased perceptions into objective, statistical fact.

But police officer opinion testimony – as the National Association of Criminal Defense Lawyers argued in its excellent amicus brief – is both increasingly common and overpersuasive. Sixty years ago, NACDL points out, law enforcement made up only 6% of prosecution experts. Now they’re the most common group – called, with mounting frequency, to testify about “classwide mens rea,” the attribution of criminal intent across entire cohorts of people. Jurors buy it, trusting not just that officers are telling the truth but that their purported subjective experience rises to objective statistical fact.

The dissenting and concurring justices offered cold comfort.

Justice Jackson, who joined the majority opinion but wrote a separate sauce-for-the-goose concurrence, observed that accused people, too, are now free to retain purported experts to offer self-perpetuating opinions about the odds of guilt. But even if more accused people could easily afford experts, the smart money isn’t on defense hired guns regularly winning credibility battles with police officers.

Marginally better was Justice Gorsuch’s observation that a slew of other evidentiary rules still demand excluding law enforcement opinions about cohort-wide criminal inclinations. Again: if the opinions aren’t “about” the defendant, they’re irrelevant and prejudicial under FRE 402 and 403. If they just replicate, or seek to displace, common-sense inferences about intent, they’re not proper expert evidence anyhow under FRE 702. And it’s hard to understand why a police officer’s summary of his own anecdotal experience, laundered as expertise and validated by the convictions that the opinion itself bootstraps into existence, clears the Daubert bar. It’s not testable, falsifiable or quantifiable.

If judges were indeed better gatekeepers, the Court’s whittling away at FRE 704 would not be so concerning. And defenders now have no choice but to focus their advocacy on the rules that Justice Gorsuch identified, and to try and produce their own experts to gainsay prosecutors’ broad claims about classwide mens rea. But that defense advocacy takes place against the real-world backdrop of a history of disappointing performance. As the NACDL brief observes, judges have historically been far too permissive of police officer expert testimony. The brief musters scholarship supporting its argument. We can hope that federal courts will insist that police do the same.