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DNA samples from thousands of convicted murderers and rapists who are not on the national database are being collected under new police powers.
Around 12,000 criminals have been identified who are on the police national computer but are not on the DNA database.
Police are now allowed by law to take a DNA sample from anyone convicted of a crime, even if it was several years ago.
A pilot carried out in Hampshire focused on the gravest crimes, such as murder and sexual assault, but none of the 167 samples found matched any of the force's cold cases.
The initial list was of 471 people, but some had died, some had moved away and others were considered very low risk.
The national operation is targeting people who have been released from prison and whose DNA has not been added to the database since it was created in 1994.
Officers will be taking the additional samples from now until next summer.
Amanda Cooper from Thames Valley Police, who chairs the DNA Strategy Board, said cases would go back to the establishment of the police national computer, which first came into use in the 1970s.
She said: ''This isn't just about the retrospective matches, it's about crimes going forward.''
Officers are allowed to force the offenders to give samples if they need to, although Hampshire chief constable Alex Marshall said no arrests have been made so far.
A final report on the scheme, called Operation Nutmeg, will be finished by next September.