Go back to the basic premises of English law and assume people are innocent until PROVEN guilty. Use the DNA database the same as fingerprints (they really are genetic fingerprints after all) and ONLY keep samples for people convicted of an offence or charged and awaiting trial. Remove and destroy all other samples immediately.
Yes it might mean we miss the odd new, never been done before, criminal – but that would be a small price to pay to restore our basic civil liberty in this area.
Why is this idea important?
Our DNA is a marker of our inner selves. It is wrong to keep such a thing on police or government files for innocent people.
Also, it is the wrong way round to keep having databases of every whatever it is – we should keep only the guilty in this case, a smaller database to manage, cheaper to build & maintain and less chance of errors.
Lastly it would save money to scrap it.