This is a crime, and one that can carry severe penalties, if left unaddressed.
For example: You are involved in a court case. You know the truth about a certain matter, which is relevent to the outcome for the opposing party. You choose to alter, conceal, hide or withold that evidence, from the court that the case is in, knowing it is important or vital information. You have committed a crime. By informing your Attorney or the Judges' office, as to that legitimate information, you may save yourself from further prosecution, fines, jail time and other legal penalties.