What confronts senators as they contemplate a vote on Supreme Court nominee Judge Bret Kavanaugh is a criminal fact finding. It’s true he faces no charges. He’s not in court, not entitled to a formal presumption of innocence, not protected by the high standard of proof governing criminal proceedings.

But the critical question before the Senate is whether Judge Kavanaugh committed the criminal assault alleged by Dr. Christine Blasey Ford. If he did—and if he then lied about it heatedly and under oath—he’s surely disqualified from service on the Supreme Court.

Those of us who hoped an FBI investigation might help settle the matter now know it delivered no such clarity. Perhaps a fuller investigation would have done so, and perhaps the White House is to blame for its scantiness. But the latter is a political question, and the former is speculation. So let’s confront the irreducible factual question now before the Senate.

First we must set aside any suggestion that lacking corroboration, Dr. Blasey’s accusation must fail. Even in a criminal court demanding proof beyond a reasonable doubt, there’s no rule a sworn accusation requires corroboration. There once were such rules. They applied specifically in rape cases and explicitly because complainants in sexual assault cases “all too frequently have ‘an urge to fantasize . . . .’”  Those rules thankfully are gone.

At all events the absence of corroboration in this case suggests little. That Mark Judge would deny having egged on and laughed at the attack alleged by Dr. Blasey is hardly surprising. Perhaps a skilled cross-examination would have shaken his denials, but we’ll never know. Nor is it surprising that others named by Dr. Blasey as present in the house at the time of the attack remember no such event. She did not tell them of the assault at the time; for them it was an unremarkable afternoon some thirty-six years ago.

We are left, then, with Dr. Blasey’s accusation. I think there are three reasons to believe her.

This is not, first of all, the lie a liar would tell. A liar would put herself and the accused in a room alone together, so none but the accused could dispute her account. She would not place the accused’s good friend in the room urging on the attack, for he predictably would deny the assault, making it a contest of two men’s words against hers.

It is secondly hard to conceive a motive that would drive a person with a quiet family life and a comfortable academic career to endanger her peace of mind, her good name, and her family’s safety by mounting a false accusation. Why would Dr. Blasey thrust herself and her family into this maelstrom by fabricating a wicked falsehood against a long-ago acquaintance?

And almost anyone Dr. Blasey’s age, looking back at the worst thing an acquaintance did to her in high school, would remember today that person’s name and what he did. Most of us experienced high school affronts far less grave than the terrifying assault Dr. Blasey described. Yet we remember the wrongdoer and his acts. Claims she could be mistaken fall flat.

Would these three reasons, taken together with Dr. Blasey’s harrowing account told under oath, warrant a criminal jury in finding guilt beyond a reasonable doubt? That is I think a close question, but it’s not the question facing the Senate.

Here the standard of proof is that governing hiring decisions. No parent would hire a man facing such a sworn accusation to babysit her children. No professor would hire him as a teaching assistant. And the Senate should not entrust him with the solemn duties and decision-making power of a justice of the Supreme Court.

A former Massachusetts assistant attorney general and assistant district attorney, George Fisher is one of the nation’s top scholars of criminal law and evidence.