that is, it only applies to new arrests, then the numbers the innocent people involved could be millions.  To penalise the innocent  is unjust and immoral because it is based on the unethical  idea that the  greater good of the greater number is reason enough to mistreat individuals. If only the DNA and fingerprints of the convicted were held the risks of gratuitous police investigations of the innocent would be greatly reduced. Nor is the injustice restricted to those with a clean criminal record. The DNA and Fingerprints of anyone convicted of a recordable crime will be held indefinitely.  That means people who have committed minor offences such as common assault  or driving without due care and attention without causing an accident (often only once in their lives) will be subject to the same risk of further gratuitous investigation based on false positives and so on  as those with no convictions who remain on the PNC.  This is disproportionate. Here is a question which I have never seen publicly posed: why are fingerprints and DNA taken from every  person arrested regardless of the suspected crime?  It is easy to see that they might be useful in the case of criminals such as murderers, burglars and rapists, but what purpose does it serve for people such as fraudsters and those convicted of dangerous driving?  It is very improbable that fingerprints or DNA  records will be useful in solving future  crimes by people who are convicted of   fraud or driving offences if