Justinian came back as Cyrus Vance

Mr Vance, in case you’re wondering, is Manhattan’s District Attorney. Yet the generations to come will never wonder about Mr Vance’s identity.

His will be a household name. For Mr Vance made the most staggering breakthrough in jurisprudence since Codex Justinianus was compiled in 529-534 AD.

Jurists, both before and after Justinian, have always struggled with the standard of proof required for criminal conviction. Most countries practising the adversarial trial system have settled on the concept of proof beyond all reasonable doubt.

And the general consensus in Britain, the US and other residually civilised places is that some forensic evidence is required to remove such doubt from the jurors’ minds.

As recently as the 18^th century, that was seen as not only protection against unjust verdicts, but also as a way of saving the jurors’ souls from the damage done by passing them. You see, in those unsophisticated times, legality in the West still hadn’t been cut adrift from its biblical antecedents.

Now that progress has severed such antediluvian links, in comes Cyrus Vance. He made a startling discovery that rape cases must be exempt from casuistic technicalities.

Commenting on the verdict in the Weinstein trial, the trailblazing Mr Vance issued a statement that flips common law on its head: “It’s rape even if there is no physical evidence. Even if it happened a long time ago.”

It took me some time to grasp all the implications of this momentous discovery. And when I did grasp them, I shuddered with fear.

What if a man’s old girlfriend claims that he raped her by way of starting the relationship all those years ago? Now, the man himself would know she’s lying. But would the police, the prosecution office and – should it come to that – jury know it? How could he prove he didn’t rape her?

Such a task would fly in the face of elementary logic: it’s impossible to prove a negative. It would also fly in the face of our justice because he shouldn’t have to prove any such thing.

The burden of proof is on the prosecution, for another feature of our law is called presumption of innocence. The defendant is considered innocent unless proved otherwise beyond reasonable doubt.

My sympathy is with the prosecutor in such a case. In the absence of any forensic evidence, be it witnesses, bruises, CCTV footage or DNA testing, the only thing he has to rely on is the alleged victim’s word against the alleged rapist’s.

Even if the claimant weeps convincingly and the defendant looks like a cad, such a confrontation can’t possibly remove all reasonable doubt from the minds of the unbiased jury.

The italicised words are the key. For a guilty verdict under such circumstances could only be passed by a biased jury regarding all possible doubts as unreasonable. In other words, the jury has to decide, or be instructed, that the woman’s word ipso facto weighs more than the man’s.

Such an unbalancing act isn’t historically unprecedented. In the Middle Ages, for example, a woman’s testimony was worth half of a man’s. Such weighing by sex went hand in hand with weighing by religion.

At the time of Magna Carta, the courts accepted an Englishman’s oath only when corroborated by eleven witnesses. By contrast, a Jew’s testimony was accepted without any further validation.

However, times have changed, and equality before the law has become the cornerstone of Western legality. And it’s this cornerstone that Mr Vance knocked out with one mighty blow.

When this happens to a structure, in this case justice, it tends to collapse. But Mr Vance is clearly driven by higher concerns than the rule of law, which is still somewhat unexpected in a lawyer.

If medieval jurists worried about the potential damage to the jurors’ salvation, Mr Vance too is driven by metaphysical desiderata. He wishes to protect and advance the currently fashionable ideology.

It doesn’t take a flight of fancy to foresee an extension of his breathtaking ruling into other, and eventually all, trials. If, say, a defendant accused of murder is obviously a nasty bit of work, he must be convicted even in the absence of any evidence. That would drive the thin end of the wedge all the way in, until the wall cracks in half.

Yes, it is indeed unfair that a rapist may go free. His victim may be reluctant to report the crime for some reason (fear, embarrassment, an attempt to blank the trauma out). Then, when years later such inhibitions no longer pertain, she does report it – only to find that the case never reaches trial for lack of evidence. Or, if the reprobate does find himself in the dock, he is acquitted for the same reason.

Yet, it’s unfair. But the law should concern itself not with fairness but with justice, and sometimes the two are at odds. Unfairness doubtless hurts its victim. But injustice hurts us all.

Every day, a criminal goes free somewhere because the prosecution doesn’t have enough forensic evidence to prove its case beyond reasonable doubt. We regret such outcomes, but also rejoice at the same time: the backbone of our body politic, the rule of law, remains intact.

Break that, and none of us will be safe from arbitrary prosecution. Having lived the first 25 years of my life in a country where a phone call from the local party secretary or KGB officer predetermined court verdicts, I can testify to the unmitigated horror of it.

There, in the Soviet Union, ideology trumped justice too. Is this the ideal Mr Vance sees in his mind’s eye? Perhaps. Or else he simply wants to keep his job in a hysterical atmosphere created by frenzied ideologues and their ‘liberal’ champions.