Does DNA evidence degenerate?
For every criminal convicted in which DNA played a part, guilty or innocent, it's now a shot at getting out. DNA evidence lost or degraded so no positive match? Judge orders a new trial, witnesses are dead or have been threatened or don't want to testify, the prosecution has no case and they decline to prosecute. "Wrongly convicted inmate freed".
Remember the Central Park Rapists? They bragged about what they had done and confessed with parents and guardians present. When the only DNA that could be tested showed another rapist was also involved they claimed that they were just innocent choirboys.