Ultimate responsibility for any homicide case in NYC rests with the precinct detective squad concerned, but the Major Case Squad has historically played a large and important role in the investigation of any homicide of an NYC police officer.

Members of the Crime Scene Unit assist the precinct detectives in the processing of a crime scene as well as determining the proper routing of evidence between the Medical Examiner's office, the NYPD Police Lab and the NYPD Property Clerk.

The Crime Scene Unit covers all of the boroughs of New York City, but is staffed with fewer than 1% of the total number of detectives in the NYPD.

The Crime Scene Unit has at its disposal many tools to process a crime scene including the materials needed to develop fingerprints, cast footwear and tire impressions, follow the trajectory of bullets fired through windows and the chemicals necessary to observe blood under special lighting conditions that would otherwise be invisible to the naked eye.

The unit is also trained to process a crime scene in a hazardous environment, for example following a nuclear, biological or chemical attack.

Each individual squad is staffed with a Lieutenant as the Commanding Officer and Sergeants to run teams of Detectives.