Evidence needs to be collected quickly in date rape cases

Anyone complaining of a sex attack in five police force areas will be asked questions and offered a series of tests during one weekend in April.

It is a response to increasing media attention of date rape cases linked to drugs like Rohypnol.

But police say the drug has never been positively linked to a crime.

The study is being sponsored by the Association of Chief Police Officers, led by its vice chair, Detective Chief Superintendent Dave Gee, of Derbyshire Police.

He said: "It is a response to the very little empirical data we have to inform the debate around allegations of drug related sexual assault.

"There is a lot of press and media hype around the issue, particularly about Rohypnol, but there has never been a single detection found in any inquiries in this country."

The jury is still out on it but the bottom line is we don't know Detective Chief Superintendent Dave Gee, Derbyshire Police

Officers in Greater Manchester, Lancashire, London and Northumberland will also be taking part in the study.

Victims of alleged sex crimes will be asked to give urine samples to be tested and will be questioned about their medical history and use of alcohol and recreational drugs.

The results will then be analysed by the Forensic Science Services.

Mr Gee said the outcome of these tests would decide the next phase of the research.

He said he was unsure if the use of alcohol and recreational drugs was part of the problem.

"Maybe. The jury is still out on it but the bottom line is we don't know," he said.

"People are turning up some days later and saying something happened but they don't know what - the evidential chain is discontinued.