As long as the matches are not being used as evidence on trials or as evidence to get warrants, the police can generate their list of leads by consulting a hamster, or by taking names out of a hat. Right? Or is there/should there be a right to not be considered a suspect on foolish motives?
Also, maybe these techniques are useful, in the sense that they allow for police to use a bad image to reduce a pool of suspects to a manageable pile that can be examined by hand.