A number of jurisdictions fought the retesting of DNA once the technology became available and cheap, mainly it seems because it was revealing to many embarrassing discrepancies. You could not just automatically apply to retest the evidence, you had to have other grounds to make the claim, etc.
the law proefssion is especially sensitive to suggestions they might have made a mistake, even an understandable one. A lot of testimony may be questionable. My favourite, any time someone “confessed” to an undercover policeman or a friendly informant (Stool pigeon) in a cell, you have to think someone is desperate to manufacture extra evidence.
The Guy Paul Morin case is famous for that. The undercover policeman insisted that Morin had confessed, although the recorder messed up and there was nothing on tape, Morin insisted he had said no such thing, and the third time around with all the new evidence, they finally acquitted him.
The usual shortcut is to get the guy pardoned, if the evidence is overwhelming. Then work on a real acquittal or whatever after he’s out. Then, if the case was particularly damning, the question is how much the state is on the hook for damages for railroading the guy.