Juries are to be told how rape victims typically respond in an attempt to dispel "rape myths" which ministers believe are contributing to plummeting conviction rates for the crime.

A panel of judges, doctors and academics will start work next month on the project, which will attempt to put together a package to inform the jury without interfering with the fairness of a trial.

The move is part of reforms announced yesterday by the solicitor general, Vera Baird, aimed at boosting a conviction rate which has dropped from 33% of reported rapes in 1977 to just 5.4% in 2005, rising slightly to 5.7% last year. A US study in 1989 found that myths affected the outcome of rape trials more than any evidence.

Jurors are expected to be told that victims may be slow to report the attack and that they may appear unemotional in the witness box, contrary to expectations.

"Juries sometimes find it difficult to understand why a rape has not been reported to police immediately when, in fact, it can take victims some time to decide to make a complaint," said Baird.

"Juries can think that she [the victim] will be upset and very emotionally raw when she relives the episode for the court when, in fact, post-traumatic stress makes people seem unemotional and almost matter-of-fact."

Ministers initially proposed allowing expert witnesses to give evidence to the jury on how rape victims behave. But that idea, which circuit judges described as a "minefield", has been shelved. The panel is expected to recommend an information booklet, a video or directions from the judge. A proposal for a statutory definition of "capacity to consent" - to deal with situations where a woman was so drunk it was questionable whether she had the power to say yes or no - has also been scrapped.

Baird said legislation was unnecessary since the court of appeal had set out in a case last March how juries should approach the issue when it quashed the conviction of Benjamin Bree, a 25-year-old software engineer found guilty of raping a 19-year-old student after a night of binge drinking.

The reforms include proposals to allow victims to substitute a videotaped interview with police for their initial evidence in court. Restrictions on the admissibility of "hearsay" evidence - occasions when the woman confided in friends or relatives - about the rape will also be removed.

Katherine Rake, director of the Fawcett Society, welcomed the proposed changes but added: "These changes will not by themselves lead to a significant improvement in the conviction rate as most cases fail long before they get to court.

"Responses to allegations of rape need to improve across the whole criminal justice system and wholesale reform is needed to tackle the failures in the investigation and prosecution of rape cases."