It is currently impossible to say with certainty how many crimes are detected, let alone how many result in convictions, due at least in part to the matching of crime scene DNA to a personal profile already on the database, but it appears that it may be as little as 0.3%—and we note that the reason for retaining personal profiles on a database is so that the person can be linked to crimes he/she commits later… It is not known how many crimes are solved with the help of the stored personal profiles of those not previously convicted of a crime… We are not convinced that retaining for six years the DNA profiles of people not convicted of any crime would result in more cases being cleared up—let alone more convictions obtained—than retaining them for three years. We therefore recommend a three year limit.
How can we have a sensible debate on criminal justice policy if the Home Secretary ignores careful reports from select committees (where his own party holds a majority), and so carelessly throws around such serious accusations?
UPDATE: Chris Pounder points to the even more damning conclusion of Parliament's Joint Committee on Human Rights:
“When asked for further information on statistics relating to individual cases, the Government has been unable to provide it. For example, we asked the Government for more information about the ACPO research which it states illustrates that 36 rape, murder or manslaughter cases during 2008-09 involved matches to innocent persons’ DNA retained on the NDNAD which were of 'direct and specific' value to the investigation. Unfortunately, the Government was unable to conduct this analysis within the time that we asked for a response… We recommend that the Government publish the details of these cases, if necessary in a suitably redacted format, or it should stop referring to them as support for its proposals."