The production arranged for Dr. Stephen A. Sands, a psychiatrist and faculty member of Columbia University College of Physicians and Surgeons to be a technical adviser for the film, and he remained on set during the filming of scenes that involved psychiatric issues. Sands was very familiar with the details of mobster Vincent "The Chin" Gigante's alleged mental illness, after studying the case during his post-doctoral training. Sands also arranged for De Niro to visit Bellevue Hospital's psychiatric unit to meet patients and psychiatrists to discuss the character's symptoms, and De Niro sometimes participated in group therapy sessions during these visits.