In a country such as ours, which values highly the presumption of innocence, it is odd of the government to announce a target for convictions. That, surely, amounts to a presumption of guilt – a presumption that the government knows how many people are guilty of a particular crime and therefore how many people the courts ought to find guilty of it. That’s not only entirely at odds with the essential spirit of English justice. It’s completely unreasonable as well.

Perhaps that is not surprising in the case of the crime in question, which is rape. The thought of rape has a way of driving out both fairness and facts – something that politicians are ready to exploit. Last week the government announced again its determination to raise what it considers a low conviction rate for rape. Vera Baird, the solicitor-general, said that it would design new “guidelines” for judges and “packages” for juries to clarify the law on consent and to dispel the many “myths” surrounding rape, which are said to keep the conviction rate so unacceptably low.

No doubt this flurry of feel-good intentions was in part a response to a successful speech that David Cameron recently made on the same subject. And on the face of it, it seems tremendously worthy and heart-warming, not to say female-voter friendly. However, it is in fact misleading and unreasonable. Rape is a dreadful crime and it is true that, of the cases reported, only about 5.7% end up with a conviction. But the facts would lead any just and sensible person to dump these self-serving plans for targets and rape starter packs immediately.

At the moment in England and Wales, of the rape allegations that women make to the police only 12% end up in court. Given that 5.7% or so of the reported cases lead to the man being found guilty, that means that 47%, not 5.7%, is the true conviction rate for rape. That sounds entirely different and relative to other crimes it is not low. It is slightly higher than the conviction rate for murder.

If the public had been fed the true conviction figure of 47%, rather than the misleading one of 5.7% or so, people would be feeling much less aggrieved. However, ill-informed grievance is grist to the politician’s mill.

As to why so few rape accusations get to court, there are all kinds of possible explanations other than public indifference to the rights of women. There may be some truth in the feminist view that policemen (and presumably policewomen) are sometimes inclined to dismiss women’s claims as exaggerated or frivolous or unimportant. If the complainants are drunk, or were drunk at the time, they may arouse prejudices in the Old Bill. All the same, the government’s own surveys point in a different direction.

According to Home Office research of two years ago, a sixth of the rape complaints that the police dropped were classed as false allegations. A quarter were dropped because of insufficient evidence or none. A third were dropped because the complainant withdrew her allegations. There are many ways of explaining those findings, but they all tend towards the same conclusion: there are many entirely respectable reasons why so few accusations of rape, true or false, get to court.

I do not want to make light of rape; at its worst it is a dreadful crime and in every case it is unacceptable. However, there does, as always with rape, seem an astonishing amount of room for doubt, even for self-doubt.

Years ago, researching this subject, I read to my amazement the results of a questionnaire in a women’s magazine, in which many readers commented that until they had answered the questions, they had not been aware that they had been raped. Call me oversensitive, but I think one would notice if one was being raped. And if one wasn’t capable of noticing at the time, how could one know afterwards?

In rather the same strange spirit, at least according to a recent Home Office analysis of the British Crime Survey, “only 60% of rape victims were prepared to self-classify their experience as rape”. This is a most odd kind of doubt. If nothing else, it suggests that the subject of rape is surrounded by irrationality.

It is hardly surprising, therefore, that when the members of a jury are confronted with a rape case, they will be both confused and cautious. It is not often easy to decide between one person’s word and another’s. It is not easy to decide what a woman really wanted at the time, if she herself doesn’t know or isn’t sure. And it can never be easy to convict a man for taking advantage of a woman he knows well and imagines is up for it, when he will receive the same minimum sentence, of five years in jail, as a sexual predator who violates a stranger. In justice there are degrees of rape and unless the law recognises those degrees, there will be no true justice in court.

As to the question of consent, and particularly consent when drunk, that is yet another can of worms. It is in the nature of many forms of rape that it would take the judgment of Solomon to apportion guilt and blame.

It seems to me that if a woman gets drunk, and is willingly spending time with a man, and appears to consent to sex, then she must in many cases bear some responsibility if sex takes place. It all depends on the details of each story, but women sometimes do give out mixed messages, as any juror will be aware. No amount of distinguished quangocrats and lawyers could dream up a guideline for every possibility.

Apart from creating different new levels for the offence of rape, from drunken errors with a friend right though all degrees of abusing a wife to attacking a stranger or a child, there is little more that anyone can do to find and punish the guilty. And given that, one wonders why the government is striking such attitudes about it. The research needed for the guidelines and packages may take a long time, so nothing needs to happen immediately.

Meanwhile, our government is seriously proposing to hand out carefully packaged material to jurors with the express intention of making them more likely to convict a certain group of defendants. Is this a rape of justice or are we consenting to it?

minette.marrin@sunday-times.co.uk

Times Recommends

• It’s the beginning of the affair
• Afghanistan: still a price worth paying
• Heroes of the downtrodden