Familial DNA and Human Rights

When we nick people we take their DNA. It’s the equivalent of taking a bit of spit.  I’d queue up to give mine as a public duty.  There is a database and it sometimes throws up a match to serious unsolved crimes.  Now some near misses are turning up,indicating near relatives may be implicated.  Some ‘Sleeper’ serial killer has turned up this way.

Does anyone have a decent explanation of the civil rights angles on this?