Am I the only person who thinks that there should be national DNA and fingerprint registers? Such databanks would ensure that many crimes could be solved quickly, and greatly limit the actions of serial rapists, killers, muggers etc. The technology exists, so why not put it to the greater good and protection of law-abiding citizens? The initial costs would be huge, I know, but surely the reduction in repeat offending would more than compensate for that.   
My fellow lefties say(shout, usually) that this would lay us wide open to 'fit-ups' by unscrupulous lawmen, but this risk has existed for centuries without apparent widespread abuse by the police, and the only winners at present are the criminals.   
Ythanside