In most felony cases a Presentence Investigation, or PSI, is completed after a defendant is found guilty or enters a guilty plea but prior to sentencing. It is up to the defendant to determine how much, if at all, they want to cooperate with the PSI process. However, the terms of most plea deals require cooperation. In most cases cooperation is useful to the defendant as it gives them a platform to share their life story and view of the case.
Once completed, the PSI will provide the judge with background information on the defendant, family life, prior criminal history, mental health factors, personal letters from employers, friends or family, defendants level of guilt for the crime, and various other factors. This gives the judge insight into the defendant's personal nature, background, and criminal history.