Karlsruhe does not allow a new trial after a final acquittal, even if there is clear evidence. This is not unfair, but follows an old, wise rule.
You could see how much the Federal Constitutional Court was struggling. A 17-year-old was murdered more than 40 years ago, and modern forensic science is now revealing that the suspect, who was acquitted at the time, was probably the murderer after all. What to do? Allow a new criminal trial, even though for a century and a half there has been a strict rule that no one should be tried twice for the same crime? That a legally binding acquittal is and must remain the last, the very last word?