Police forces in England and Wales have begun a large-scale operation to collect DNA samples from about 12,000 serious offenders who are not on the national DNA database.
Operation Nutmeg will see officers collect swabs from sex offenders and murderers living in the community.
Criminals are often not on the database if they were convicted before 1994, when sample-taking became routine.
The scheme has been launched after a successful pilot exercise in Hampshire.
Police hope the collection of thousands of new samples could help to solve so-called cold-cases, where a new sample is linked to a past crime.
Speaking at a briefing on Thursday, Amanda Cooper, director of information, science and technology at Thames Valley Police, said officers would approach individuals between now and next summer to collect the samples.
Police forces have been given lists of offenders living in their areas and will work though them to collect the samples.
The lists have been drawn up based on information from the Police National Computer, which was first used in the 1970s.
Alex Marshall, the chief constable of Hampshire police, said 167 samples were taken from a list of 471 convicted criminals during the pilot operation.
Some of those on the initial list had died or moved away from the area and some were considered very low risk.
No one was arrested in connection with the pilot, meaning officers had not needed to use powers under the Crime and Security Act, to force offenders to give a DNA swab.
While none of the swabs collected in Hampshire could be linked to any "cold cases", Ms Cooper insisted it was "only a matter of time" before such a case was solved in England and Wales through the efforts of Operation Nutmeg.
But she added: "This isn't just about the retrospective matches; it's about crimes going forward."
Nick Pickles, from campaign group Big Brother Watch, has accused police of "diverting resources" away from current investigations.
He said: "Members of the public will expect the police to be pursuing active investigations and in the overwhelming majority of these cases the people having their sample taken will not be suspected of any new crime.
"Diverting resources away from following up current leads to track down people based on convictions that may be decades old is a questionable strategy at a time when the police are already overstretched," he added.
The DNA details of over five million people are currently stored on the national database.
A full report on the operation is expected to be published in September 2013.