As the arraignment nears in People of the State of New York v. Donald J. Trump, our own thoughts keep coming back to Nancy Pelosi. The former speaker greeted news of his indictment by declaring that “everyone has the right to a trial to prove innocence.” The formulation was, not to put too fine a point on it, completely ass-backwards. No person in America has to prove his innocence in criminal court. The sole burden of proof of a crime in America lies on the accuser.

This is the thing to remember in respect of President Trump. We are not so sanguine about his chances of acquittal as others we have read. After all, some 85 percent of Manhattanites who voted in 2020 voted for Mr. Biden. Nor are we as inclined as others we’ve read to brush off the charges as frivolous. It’s not nothing to be convicted of a misdemeanor, and if a jury finds the former president guilty of a felony he could yet end up in prison.

No laughing matter. We are, though, concerned in respect of due process. This starts with the business about burden of proof. This concept arose, and prevailed for centuries, in the Roman Empire as onus probandi. A trial began when a claim by an actor, or plaintiff, against a reus, or defendant, came before a judex, or fact-finding judge. In Roman law, Harvard Law’s James Thayer writes, “the proof, the burden of proving, belongs to the actor; it cannot shift.”

The defendant in Roman law, Thayer writes, “awaits the action of his adversary; and it is enough if he simply repel him.” The defendant had “no duty of satisfying the court; it may be doubtful, indeed extremely doubtful, whether he be not legally in the wrong and his adversary legally in the right.” Yet a defendant may “gain and his adversary lose,” Thayer writes, “simply because the inertia of the court has not been overcome.”

Thayer, writing in 1890, saw that the Roman ideal of the onus probandi was still at the core of the trial process, though in the intervening centuries an important distinction arose between civil and criminal cases. While Rome had no state prosecutions, modern civil trials have come to be decided by the less strict standard of a “preponderance of the evidence,” meaning a plaintiff need only prove a defendant is more likely than not liable.

In criminal cases, the onus probandi rests on the state and “proof beyond a reasonable doubt” is a “fundamental normative precept of the Anglo-American conception of justice,” the Yale Law Journal has noted. The Supreme Court holds that the 14th Amendment shields the accused in state courts from “conviction except upon proof beyond a reasonable doubt of every fact necessary to constitute the crime with which he is charged.”

Which brings us back to Mrs. Pelosi’s distorted idea of the trial process. “No one is above the law,” she condescends to Mr. Trump, urging him to “peacefully respect the system” while he tries to “prove” his “innocence.” Justice William Brennan saw why the burden of proof rests with the state: so that “the moral force of the criminal law not be diluted by a standard of proof that leaves” any “doubt whether innocent men are being condemned.”

Such a high bar for proof by the state in a criminal prosecution, the Nine found in a 1970 case, In re Winship, is essential to the maintenance of a “free society.” It was “important,” Brennan wrote, “that every individual going about his ordinary affairs have confidence that his government cannot adjudge him guilty of a criminal offense” — without first “convincing a proper factfinder of his guilt with utmost certainty.”