‘NOT guilty, but don’t do it again”. That was how some lawyers used to refer to the “not proven” verdict in Scottish criminal trials. Unlike in England, juries in Scotland have three verdicts from which to chose: guilty, not guilty and not proven. Now, rape campaigners are calling for the not proven verdict to be scrapped on the grounds that, according to Sandy Brindley of Rape Crisis Scotland, it gives the jury an “easy option” in difficult cases. Around one-fifth of acquittals are not proven.

It’s not easy to justify this apparent anomaly in criminal law. We know in any criminal trial the test is whether or not the prosecution has proved its case “beyond reasonable doubt”. If not, juries have to acquit. Which means not guilty – there is no middle way in the law. So why, in effect, have two not guilty verdicts?

Some lawyers, like Derek Ogg QC, have argued that logically it is the “not guilty” verdict that should go. This would concentrate jurors’ minds on deciding whether or not the prosecution case had been “proven” beyond reasonable doubt. This is apparently how it was in Scottish courts in the 16th century. The “not guilty” verdict was reintroduced in the 18th century.

However, many lawyers used to argue that the not proven verdict harmed the accused, not the accuser. Having a jury rule that the case against you was “not proven” might suggest that you got off on a technicality, or that the prosecution just hadn’t got its act together. Defence lawyers argued that guilt should be expunged by an unequivocal declaration of not guilty – meaning he or she really, really didn’t do it. The late former Scottish Secretary, Donald Dewar, moved a Commons Bill in 1969 to have the “bastard verdict”, as Sir Walter Scott called it, scrapped. But this wasn’t because he thought it would necessarily make rape convictions easier.

Not proven still has its defenders. Some say abolition would undermine Scots law and that we shouldn’t be importing an Anglicised system on a wave of emotion. It is good for juries to have more than one option so that they can express a degree of doubt, or qualification. Brian McConnachie QC, the former President of the Criminal Bar Association, has pointed out abolishing it could have unintended consequences. As we discovered during the debate about scrapping corroboration in rape trials, getting rid of one anomaly often creates a raft of new ones.

In Scottish jury trials there need only be a simple majority for conviction, eight to seven in a 15-person jury. In England the test is much stricter – there are smaller juries and the majority has to be 10 out of 12. If not proven is dispensed with, many would argue that the Scottish majoritarian system would have to go too. This might actually make it harder to get rape convictions.

Indeed, you could argue that not proven gives an “easy option” the other way – in favour of the accuser. It allows juries who believe the “victim”, but are not convinced by the prosecution’s handling of the case, to say: “We think he or she probably did do it, even though the evidence isn’t conclusive.” This arguably sends a signal to the civil courts that this person might be guilty on the balance of probabilities. Civil courts are less strict on the need to prove “beyond reasonable doubt”.

This is actually what happened in the case of Miss M, the rape victim who has been arguing for not proven to be scrapped. She made legal history last month by taking the not proven verdict against former student Stephen Coxen to the Personal Injuries Court in Edinburgh, where it was effectively reversed. She was awarded £80,000 in damages. Of course, that raises further questions about double jeopardy. If someone is found not guilty in one court, does it makes sense for them to be found guilty in another?

If you accept the #metoo doctrine – “always believe the victim” – then you don’t really need trials at all. However, this causes problems when the wrong people get accused. When one of the leading figures in the #metoo movement, the Hollywood actress Asia Argento, was accused in August of statutory rape of an underage boy in California, her defenders insisted that she should be given the benefit of “due process”, and be innocent until proven guilty. This was correct. The rush to judgment was wrong and unfair – even though she reportedly gave the “victim” $380,000 to settle the claim privately.

The problem with sexual assault and rape is that they often involve difficult cases relying, in the absence of corroboration, on “he said/she said” and the credibility of the parties involved. I have never sat on a rape case jury, but I’ve spoken to many who have, and they tell me the cases often involve alcohol and vague and muddled memories. It is probably the case that too few rapists are being punished. But tipping the scales in favour of the victims doesn’t always work.

The justice system in England has been rocked by the collapse of a succession of highly-publicised rape trials in which the police withheld, or failed to disclose, evidence crucial to

the defence. The former head of the Crown Prosecution Service, Alison Saunders, had to make a formal

apology, and then resigned last month, after a review covering just two months of English rape cases found that 47 had to be halted because the police had failed to hand over evidence of innocence. The police insist that they weren’t trying to rig the prosecutions. But the head of the Metropolitan Police, Cressida Dick, has since issued new guidance saying that “complainants” in rape and sexual assault cases should be listened to, but not automatically believed. “It’s not all about the victims” she said.

Justice is hard. The debate over not proven has been grinding on for a long time. Holyrood’s Justice Committee has said that the dual acquittal is on “borrowed time” –which I suppose is itself a kind of not proven verdict. Scrapping the Scottish verdict

is beginning to look well nigh inevitable. But whether or not this will increase rape convictions is, well, not proven.