DNA should be taken from crime scenes, checked against the criminal database and, if not identified, stored pending identification.
The taking of DNA from people who have merely been arrested should only be to check two things. Does it match any unidentified crime scene record? If so, the person is a suspect in a crime. Does it match any criminal record? If so, does this match the identity they purport to be and are they marked as wanted or jail? If neither of these things apply, the data should be destroyed.
The state has no right to our DNA. A universal DNA database will not stop crimes taking place. DNA evidence does not make convictions water-tight. It can be faked and planted, the same as any other evidence.
The Government's faux-position of 'we have no plans' to create such a database is not worth a tinker's cuss. Purposefully keeping hold of DNA samples from innocent people - many of them children and victims of crime themselves, is indefensible.
The panacea of a DNA database is offered up within a context of massive failure to effectively punish the convicted guilty. The DNA database is mainly helping the police identify convicted criminals who have been released from jail, when they shouldn't have been. The most glaring failure of the criminal justice system is the disregard of the two most important principles in dealing with crime: Punishment and protecting the public.