Forensic scientists have the full DNA profiles of more than 100 suspected rapists behind attacks in London going back more than two decades.
The profiles were uncovered during a re-examination of documents and material from archives about unsolved crimes from the 1980s and 1990s using forensic techniques not available at the time. One of the suspected attackers is believed to be responsible for at least two rapes.
Their identities remain unknown because there is no match on the national DNA database – the second largest in the world – which contains more than five million samples from crime scenes or individuals arrested or detained by police since 1995.
Detectives said the suspects are likely to be caught only if they are detained for a new offence and the link is discovered after a DNA swab is taken. They cited the case of Tabir Ali, a serial sex attacker who broke into a home and subjected a mother to a horrific ordeal at knifepoint. He was finally jailed 16 years after the attack when a DNA match was found after he was involved in a domestic incident in 2007.
"It's potentially 100 guys sitting at home that one day could get a knock on the door," said Detective Inspector John Foulkes of the Metropolitan Police's rape-review team. "But it may be that they are dead or spent a very short time in the country and left."
His unit has over the past five years examined 4,500 unsolved sex attacks covering 1988-90. The team of eight detectives has already secured five convictions this year. It has now started to re-examine cases from 1991. Its latest success saw the so-called "M25 Rapist", Antoni Imiela, found guilty last week of raping a woman on Christmas Day in 1987.
Although samples were retrieved at the time, a DNA profile was obtained only in 2009 when they were retested. Imiela, who was told that he was likely to spend the rest of his life behind bars, had already served eight years in prison for the rapes of seven women and girls between 2001 and 2002 and had been eligible for parole.
The cases have highlighted the technological advances which have seen DNA obtained from ever-smaller amounts of potential material kept in the freezers of the state-run Forensic Science Service (FSS) – which is being closed on financial grounds – and in police storerooms. The archive has been reprieved so it can be used by inquiry teams investigating historical cases.
Earlier this year, one of two men convicted of the murder of Stephen Lawrence was linked to the crime by a spot of blood measuring less than a millimetre across, which was found soaked into his jacket.
Detectives working for the rape-investigation team, based in west London, have gone back through files to identify whether there is potential material – such as swabs, or scraps of clothing – that can be retested. They are then sent to laboratories for examination using more-advanced techniques.
"It's a kind of weeding process... it's whittling them down to cases which are suitable to look at forensically," Detective Sergeant Mick McInerney said.
They are then compared with other information on the database. If a match is found, detectives attempt to build the case and find the victims – forcing them to confront again the circumstances of being raped by a stranger. In most cases, the women agree to help police to pursue their case. "Every single case brings some closure for people who are waiting for years and years to find some justice," DI Foulkes said.
Snared by science: Four rapists caught by DNA testing
Robert Edwards Was jailed this month for eight years for a rape committed 21 years ago. A DNA match was made after the re-testing of old lab samples.
Antoni Imiela Already in jail for a string of attacks that saw him named "the M25 Rapist", he was sentenced to a further 12 years last week for a 1987 attack. DNA tests linked him to the crime.
Daniel Dolen Serial rapist was convicted this year after a victim came forward following publicity over other attacks. Dolen had tried to rape the woman, then aged 14, in a park.
Charlie Ward Jailed for five years in February for the rape of a young woman in 1986. He was already serving time for another attack solved after a cold case review.
The number of unsolved sex attacks examined by the Met's rape-review team.