If I go along with your thinking, we might be left with the impression that the police wouldn't use DNA information if they thought it was going to remove a person from their suspect list. Having worked in that for 30 years, I have never in those 30 years known a police officer--and it would be a criminal offence--not to use evidence that would exonerate the accused.
Evidence of meeting #6 for Public Safety and National Security in the 40th Parliament, 2nd Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was offences.
A recording is available from Parliament.