Jules Epstein

The not-so-veiled threat made by Florida Rep. Matt Gaetz to Michael Cohen in a tweet earlier this month—“Do your wife & father-in-law know about your girlfriends? Maybe tonight would be a good time for that chat. I wonder if she’ll remain faithful when you’re in prison. She’s about to learn a lot.”—created an uproar and ultimately an apology of sorts. Whether the congressman’s words were meant to intimidate is a political and legal question, one intertwined with issues of intent and the protections granted by the Constitution’s speech and debate clause. But whether the cheating is pertinent depends on evidence law.

In a trial, or in a Congressional hearing, it is fair to test a witness’ credibility. Congress has no rules of evidence—but those applied at trial are informative and help the discussion of whether Cohen’s having girlfriends while married is fair game.

At trial, witnesses are required to take an oath or otherwise affirm that they will be truthful. They are then asked to tell their story or otherwise share the information that they hold. To assess whether the oath has indeed produced accurate testimony, one permissible attack is to show that the witness has the character trait of being dishonest.

The theory is based on a three-step reasoning process: some proof of dishonesty is offered; that proof is ruled sufficient to show that the witness has the character trait of being dishonest in general; and then the jury is permitted to conclude that if the witness is dishonest in general then it is likely that there is dishonesty in the story being offered at trial.

The question for Congress involves the second step. Assuming it can be proved, or Cohen will admit, that he committed adultery, is that the type of act that proves his “character”—a tendency to be dishonest about all things? The answer—at least in the courtroom—is “no” in Pennsylvania and “maybe” in federal court trials.

Why the difference, and why the “maybe?” Pennsylvania’s Rules of Evidence permit a witness’ dishonest character to be shown by proof of crimen falsi convictions—a record of theft, forgery, or other crimes of deception—or by testimony about the witness’ reputation for being dishonest. The theory of the former is that even a single criminal act shows a general tendency to be untruthful; and the idea of reputation is that if many people describe the witness as dishonest there must be a good reason for it.

But Pennsylvania did not adopt one Rule of Evidence that the federal courts apply—Rule 608(b). That rule permits a witness to be questioned about past conduct—e.g., cheating on a bar exam, having multiple Social Security numbers, committing fraud in government contracts—if it is “probative of the character for … untruthfulness … .”

And the “maybe?” There is no scientific measure for whether any one act, or even a series of acts, predicts or proves the character defect of being dishonest in general. If a person cheated on an exam, or stole from the grocery, there is no certainty and no ascertainable probability that the same person would testify dishonestly under oath. The decision is in the eyes of the judge—and it is a guess. And at least as of 1999, many reported decisions said that adultery did not prove dishonest character.

A Congressional hearing does not apply the rules—but the committee can decide topics are off-limits or of little value. Evidence law gives some, but not much, guidance.

Cohen is a self-described liar. His remarks prepared for Congress confess this: “For those who question my motives for being here today, I understand. I have lied, but I am not a liar. I have done bad things, but I am not a bad man. I have fixed things, but I am no longer your ‘fixer,’ Mr. Trump.”

So whether he also engaged in adultery may be of little moment, because his conduct as an attorney for Trump already impugns his honesty—but his claims should also be judged by whether they can be corroborated and his motive(s) to testify now.

Jules Epstein is a professor of law and director of advocacy programs at Temple University’s Beasley School of Law. He is a former partner at Philadelphia criminal defense and civil rights firm Kairys, Rudovsky, Messing & Feinberg, where he remains of counsel. Epstein teaches criminal law and evidence courses at the university.