Ministers were today publishing proposals to boost the number of people convicted of rape.
The proportion of rape allegations which lead to someone being punished has sunk to an all-time low, despite long-running Government efforts to boost results.
Changes to the rules on what can and cannot be said in court were expected to be among proposals contained in a consultation paper today.
Ministers will propose allowing juries - rather than judges - decide if a woman was too drunk to consent to sex.
There will also be an attempt to de-bunk jurors' prejudices about rape victims, by allowing experts to say how victims tend to react after a sex attack.
"We may need to redefine the law on a person's capacity to consent to sex," said a Government source.
"Currently the law clarifies that being asleep or unconscious would hinder someone's capacity.
"This could be redefined to take alcohol and drugs into account.
"We think this plays a significant role in why the conviction rate is so low."
Solicitor General Mike O'Brien has said he will propose allowing "generic evidence" about rape victim's behaviour to be heard in court.
Director of Public Prosecutions Ken Macdonald suggested the move last October to "challenge the myths" about victims who claim they have suffered rape or other sexual attacks.
For example, jurors often find it hard to believe that a rape victim would suffer no physical injury, or understand why battered wives often return to their abusers, he said.
Also, jurors sometimes find it difficult to understand why a victim might not report a rape for many weeks.
The United States, Canada and Australia already allow juries to hear evidence from psychologists and other experts about why victims may behave in a certain way.
The Government source said: "Part of this is to tackle the stereotypes and myths that persist."
Another new move proposed in today's document would allow tapes of an adult victim's very first police interview to be shown to jurors.
Currently, the recordings can only be used in cases where the victim is under 18.
Officials believe that allowing jurors to see the tapes would help paint a truer picture of the victim's emotional state soon after the rape.
Jurors may then get a better understanding of the enormity of the experience, the source said.
The paper will be published by the Home Office, Department for Constitutional Affairs and the Attorney General's office later today.
Currently, only 5.6% of allegations lead to a rapist being punished.
Home Office researchers have found there is a "culture of scepticism" towards rape victims among police and prosecutors, which leads victims to lose confidence in the system.
In 2004/05, there were 14,002 allegations of rape reported to police by both male and female victims.
But in the the 2004 calendar year there were just 791 convictions.
Only 14% of allegations reach the trial stage, where about half of defendants are acquitted.
Mr O'Brien said the number of complaints of rape had gone up sharply, but the number of convictions had only risen slightly.
"An awful lot of people who are committing rapes are getting away with it," he told BBC Radio 4's Today programme.
He said part of the problem was the difficulty of getting a conviction.
"Usually only two people are present when a rape occurs and there is sometimes a lack of forensic evidence or other evidence which may convict someone."
Mr O'Brien said it was particularly problematic when the alleged rapist was known to the victim.
He said there was no suggestion men would have to be able to produce documentary proof of consent.
"That would be nonsense," he said.
"What we need to do is make sure that where alcohol has been consumed and it has affected the capacity of the victim then that matter should be put before the jury."
Mr O'Brien pointed to a number of cases where judges had decided that because a woman had been intoxicated her evidence was "hazy" and the matter should not be put before the jury because she could not say "with absolute certainty" that she did not consent.
Mr O'Brien said of 14,000 rapes reported last year only one in 20 resulted in a conviction.
He said the moves would not affect the overall burden of proof.Reuse content