In New York one may file a motion to vacate a conviction even after an appeal was denied. A person convicted of a criminal offense after a trial who has exhausted his appeals may still file what is commonly referred to as a “440” motion back in the original court where he was convicted. Many times “440” motions are based upon newly discovered evidence.
Briefly, under CPL 440.10(1)(g), a court may vacate a conviction where new evidence has been discovered after trial, which could not have been produced by the defendant at the trial and such evidence creates a probability of an outcome more favorable to the defendant. Furthermore, the defendant must file his motion with due diligence after discovery of the new evidence.
Generally, however, such “new evidence” cannot be mere impeachment evidence. In other words, such newly discovered evidence cannot simply be evidence that could have impeached the credibility of a prosecution witness. However, this is not an absolute rule. A court can vacate a conviction where the “key” prosecution witness lies at trial about prior criminal activity or other bad acts committed by him prior to him testifying. In cases where courts have vacated convictions on such grounds, the witness who lied was the key or primary witness against the defendant and the case hinged on that witness’ credibility.