I'm not sure I buy it. Police need a warrant to get dna evidence from a suspect, but warrants can and often are contested. If the system had any false positives or wasn't a perfect match a good attorney would be able to argue there are no grounds for the warrant.

If the fuzz had other evidence like an unverified alibi or evidence putting the suspect in the area that would probably be enough for a judge to issue a warrant, but if the dna photo was the only evidence I'd say it's dicey at best if tested.