If, after sentencing, you provide substantial help with another criminal case, sentence reduction is possible. For this to work, the prosecution or the government files a motion with the court asking for reduction. The time for seeking reduction is usually within a year of when the judge announced the sentence in court. There's an exception, though. 1  Your help involves new information.  You gave information to the prosecution within one year after sentencing, but the information wasn't useful until later on.