Police DNA is on a SEPARATE database
Which is why the police can say 'no don't use our DNA' and because it is on a separate database it is not used.
But if it's truly anonymous, then why would they object? You couldn't tell an officers DNA from a criminals DNA?
And I know it's tempting to talk about innocent people and crims, and somehow the crims have no rights, but do we really lose all our rights? Even for dropping litter?
If I come to you with an application 'I want to take random samples from the database and sell companies the right to check which of their employees are in the database', is it still anonymous data then?
What if I want to take random samples from shop doors so I can tell insurance companies how many people in that area are on the database?
What if I tell you one thing to get hold of the data and use it for a different purpose later? You know, like when you obtained the DNA in the first place then used it for a different purpose later. What then? Once it's out of your hands you don't know and can't control how it is used.