DNA

The British government has rejected calls from senior police officers for a compulsory DNA database following two high profile murder convictions - Suffolk serial murderer Steve Wright and Mark Dixie, who murdered teenage model Sally Anne Bowman.
Both men were captured because their DNA was taken after unrelated offences, hence the recent calls for universal registration to the database.
The current DNA database, which covers England and Wales, contains around 4.5m profiles - routinely taken from criminal suspects after most arrests and is already the largest of its kind in the world.
Mandatory DNA database rejected

While I'm glad the idea of a mandatory DNA database has been rejected, one's DNA sample remains indefinitely on the current database even if one is subsequently released by the police. Our law states "innocent until proven guilty", not vice-versa.
Furthermore I would have reservations on the security of the database. This government is already in trouble trying to protect our current data anyway, and there's no telling what agenda a future government might have - for example, monitoring people whose DNA "suggest" aggressive tendencies, or tagging the entire population at birth.
We could be on the road to this scenario....