Factual errors: Carlos Nieto stats in several episodes that he was a medic in the marine corp. This is in fact impossible as the marine corps has no medical staff of its own. All medical positions for the marines are in fact U.S. Navy Corpsmen.
Crew or equipment visible: In several episodes, cameras and equipment attached to the police cruisers and ambulances are visible in reflecting buildings and passing car windows, as the camera view shows the cast member in the far seat of the vehicle from where the camera is mounted.
Errors in geography: The 55th precinct building is nicknamed "Camelot" because it is supposedly located at the intersection of King St. and Arthur St. This is impossible because while King St. is located in Manhattan, Arthur St. is in Queens.
Factual errors: In several episodes, the ambulance that is often used by the paramedics has a license plate number of BN6-30L. In New York, that would be a passenger plate number, also, FDNY ambulances use official plates.