Daniel Hannan is an MEP for South-East England, and a journalist, author and broadcaster. His most recent book is What Next: How to Get the Best from Brexit.

They’re both telling the truth. That’s the only conclusion I draw from the whole business. Christine Blasey Ford has no doubt that Brett Kavanaugh assaulted her when they were teenagers. Judge Kavanaugh has no doubt that he is being wrongly accused. Memory, as any psychologist will tell you, is a treacherous thing.

In culture wars, of course, equivocation is seen by both sides as enmity. The row over Kavanaugh’s nomination is not about what happened 36 years ago, not really. In a textbook illustration of confirmation bias (the term is unusually apt here), conservatives and liberals start from their conclusions and work backwards. Those who approve of Kavanaugh’s politics are convinced that he is a victim of left-wing smears. Those who disapprove are convinced that he is a liar.

When I say “textbook illustration”, I mean it literally. Years from now, l’affaire Kavanaugh will be taught to psychology students as a case study in tribalism, an unusually vivid example of how human beings fit facts to their prejudices. One or two left-wingers may believe that the presumption of innocence should apply in this case, and one or two right-wingers may oppose Kavanaugh’s nomination. But I’d say that there is a 90 per cent correlation between Americans’ political opinions and the version of events they believe.

Confirmation biases are subliminal. People don’t consciously say to themselves, “I shall discount or filter out reports that challenge my political preferences, while exaggerating and dwelling on reports that sustain them”. They genuinely believe that theirs is the only fair-minded interpretation. It follows, in their minds, that their opponents – who manage to draw opposed conclusions from the same data – must be liars or fools.

Listen carefully, though, and you hear marginal voices at both ends that give the game away. Some Republicans, having supposedly taken their stand on due process, then add that you shouldn’t disqualify an otherwise excellent candidate because of something that he might have done as a teenager. In other words, deep down, they’d back him even if he were guilty. Equally, some Democrats argue that his angry response to the accusations should bar him regardless of their truth. In other words, deep down, they’d reject him even if he were innocent.

“Not only do women like Dr. Ford, who bravely comes forward, need to be heard, but they need to be believed,” says Senator Mazie Hirono of Hawaii. “I just want to say to the men in this country – just shut up and step up. Do the right thing for a change.” Got that? Whether or not Kavanaugh is technically guilty, his masculinity constitutes a sort of meta-guilt. Even more flagrant was a commentator called Ana Marie Cox whom I happened to catch on MSNBC. “We need to judge Brett Kavanaugh, not just by what he may or may not have done, but how he treats a woman’s pain,” she said. “I don’t think Brett Kavanaugh takes women’s pain very seriously, and I know that because of the decisions he’s made as a judge.” In other words, failing to empathise with someone who is accusing you, even if the accusation is false, disqualifies you every bit as much as if it were true.

For what it’s worth, I’d expect anyone who is falsely accused of a serious offence to be outraged. Judge Kavanaugh might be feigning the outrage, of course, but to argue that his anger itself proves his unfitness for office, as several liberal commentators have done since his hearing, is preposterous. Judges are expected to be emotional in their own cause – that is precisely why they have to recuse themselves when there is a clash of interests.

Is there any way of telling who is right? We can, I think, assume that Dr Ford would not be putting herself through this unless she were absolutely certain of her story. (The lack of interest from both sets of partisans in the well-being of the two principals is one of the sadder aspect of the whole affair.) Yet Kavanaugh’s defence also rings true, and the charges against him – depending on a single account, with no corroborating evidence even though witnesses were supposedly present – would be thrown out if this were a criminal case.

Sure, there are some holes in the testimony of both parties. How could there not be? If you were trying to piece together something that happened 36 years ago, you’d get things wrong too. That’s one of the reasons that the United States, like many common law countries, applies a statute of limitations to certain offences.

Which brings us to the essential problem: human memory is deceptive. It doesn’t stow our experiences in some cerebral filing system. It works on the basis of loose associations, rules-of-thumb, approximations. Even the most cursory reading of neuroscience has left me horrified at the idea that witness statements play such a large role in our criminal justice system. In controlled tests, psychiatrists found that courtroom recollections could be biased by, for example, small differences in the way that questions are asked.

Kavanaugh might seem to have the greater incentive to repress an unflattering memory. His critics are particularly keen to establish, if they can, that he was a heavy drinker in those days, which would call his recall further into question.

But Dr Ford’s recall is not perfect either. Even where recent events are concerned – how her therapist’s notes ended up in the hands of the Washington Post, how her letter requesting anonymity surfaced in the media – she draws a blank. As for the events in question, as her critics endlessly point out, she has little recollection of where she was, how she got there or who else was present.

Dr Ford is a psychology professor. She knows about the limitations of memory. She also knows that vivid memories can sometimes – as she says happened here – be repressed and then revived. “The neurotransmitter encodes memories in the hippocampus so that trauma-related experience is locked there”, she told the Senate.

That, though, brings us no closer to a resolution. Trauma is no guarantor of perfect recollection. In 1984, a 22-year-old student called Jennifer Thompson-Cannino was raped by a man who broke into her flat. Helplessly, she tried to concentrate on remembering his face: “I was just trying to pay attention to a detail, so that if I survived I’d be able to help the police catch him.” She later picked a suspect out of a photo line-up and, again, in a live line-up. But she had the wrong man. Ronald Cotton spent more than ten years in prison before he was definitively acquitted by DNA evidence. (The two later became friends, and toured the United States campaigning for reforms to the criminal justice system.)

I realise how unsatisfying this sounds, but the fact is that, in the absence of further evidence, we will never know whether Dr Ford has identified the right man.

So where does that leave the confirmation? Here I come off the fence. Not about Judge Kavanaugh – he may or may not be guilty – but about due process. The presumption of innocence should not be some empty piety. One of the nastiest aspects of politics is that this principle is often reversed when the headlines are bad enough. When Nigel Evans was falsely accused of sexual assault, for example, he lost the Deputy Speakership and a hefty chunk of income, and was never compensated. Ministers have often had to resign over ugly but unproven charges (Damian Green being the most recent example).

Yes, it happens, but that doesn’t make it right. We are talking here about an appointment to the highest court in the United States by the nation’s supreme counsel. The Senate, of all bodies, should apply the principles on which American justice rests. And one of those principles is that a conviction requires evidence beyond reasonable doubt.