Juries, and the right to a fair trial, are under threat from the left. The latest attack came from Ann Coffey, the Labour MP for Stockport, who believes that we should consider abolishing juries in rape cases. A few months ago, the tax barrister Jolyon Maugham QC – no friend of the current Labour leadership, but something of a weather vane for more moderate left-wing thinking – floated the same idea.

Coffey's argument is that 'juries view evidence through the lens of prevailing stereotypes shared with the wider community.' As a result, she says, 'the most common cause of unsuccessful prosecutions in rape prosecutions is jury acquittal'. Her suggestions to resolve this include the idea that jurors in rape cases should be 'vetted for preconceived bias.' Another is that they should be abolished altogether in rape cases.

It is now almost an article of faith among some that whenever anyone is acquitted of a sexual offence, is is these prevailing stereotypes and 'rape myths' which are to blame. Coffey, dutifully trotted some of them out:

A woman who has drunk a lot cannot complain if she is raped,

It is rape only if someone has injuries,

Real rapes are done by strangers in alleyways,

Rape is a crime of passion

Women invite rape by what they wear.

'Defence lawyers,' says Coffey 'play up (such) myths in an attempt to rubbish the character of the witness.'

Yet if there was a 'rape myth' it is that these stereotypes are routinely employed in a court of law. Defence lawyers are not allowed to simply 'rubbish the character of the witness.' Specific and relevant instances of 'reprehensible behaviour' can sometimes – with the permission of the judge – be put to witnesses, but if advocates attempt to 'rubbish' anyone's character, then one of at least three things will almost certainly happen:

They will be stopped from doing so – probably very sharply – by the judge.

Their own client's bad character will become fair game for the prosecution.

The jury will turn against them: jurors tend to hate bullying advocates, a fact drummed into young barristers throughout their training.

Another criticism Coffey has is that 'it is challenging for juries to judge whether the defendant had a reasonable belief that consent was given, especially when drink was involved. That is where myths and stereotypes kick in.'

Of course this is a challenging question to ask. But enquiring about what a complainant was drinking immediately before an alleged rape is often entirely proper. Someone who is insensible cannot lawfully consent; but someone who is simply drunk may be less inhibited and thus more willing to consent to sex than they would be if they were sober. Where consent (or, for that matter, memory) is in issue, asking questions about a complainant's intoxication is not exploiting a rape myth, it may well be an essential professional duty. Curiously enough, no-one ever objects when the prosecutor puts it to a defendant that he might have acted out of character because of his intoxication.

Some other 'rape myths' are straw men: surely only a very few people believe that the absence of injuries necessarily indicates consent, or that 'real rapes' only happen in dark alleys?

Of course, any jury is likely to contain a mixture of those inclined to believe complainants and those more inclined to give the benefit of the doubt to defendants. Jury vetting intended to weed out the latter in order to leave the former – that is people with prejudices like Coffey's – would no doubt increase conviction rates, although it would do so by the conscious creation of biased juries. That is something that even the currently supine guardians of human rights in Strasbourg might consider rather unfair.

And though Coffey may not like to admit it, I am afraid she does have prejudices. She claims – indeed it is a pretty important part of her argument – that 'the CPS asserted in 2012 that only three per cent of the 1,149 cases heard may have been malicious.' The implication of her argument seems to be that 97 per cent of rape 'cases heard' are genuine. But in fact the research to which she refers (which was conducted in 2008 and 2009) did not relate to 1,149 rape cases heard in court; it was a far more general study about attrition in the criminal justice system. Only 299 of the cases in the survey were rapes, and 558 were non-sexual allegations (GBH). The study looked at the many different reasons why allegations (both sexual and non-sexual) do not result in either an arrest, a charge or a conviction. The 'three per cent malicious' estimate is simply the lowest among many estimates of a figure that is itself unknowable, and which the research was not investigating anyway. Even as an attempt at cherry-picking Coffey's use of it is pretty abysmal.

Misleading statistics, often based on misunderstood or misquoted surveys are the stock in trade of those who want to undermine the jury system. Unless robustly called out – a tiring and time-consuming business – they become rape myths at least as pernicious as any other. Once you swallow the prejudice that there is a only a three per cent chance that a rape defendant is innocent, you have already reversed the burden of proof. The purpose of a rape trial then becomes not to decide guilt or innocence, but simply to process the guilty 97 per cent, with perhaps a rare exception when a defendant is able to prove his innocence beyond the reasonable doubt of a deliberately biased tribunal.

A future Labour government may be very receptive to the abolition of juries in rape cases. It would be taken up by many on the left as a progressive measure to help rape victims. What's more, because jury trials are more expensive than judge-only trials, it would be enthusiastically implemented by a civil service long inclined to seeing juries (and even legal representation itself) as a dispensable luxury. Once rape juries have gone, juries in all other cases will not be far behind.

Matthew Scott is a criminal barrister at Pump Court Chambers