OIS investigations seek to preserve the scene and eyewitness testimony, while also gathering resources to document the incident. The investigations can be conducted by two types of police teams: special investigative units which cover the criminal aspect of the case, and internal affairs investigators who are concerned with the officer's conduct. Homicide and physical evidence investigators are supported by a non-sworn scientist at the scene of the shooting. Because of the potential for civil and criminal suits, there are separate and overlapping responsibilities borne by the various parties. Expeditious handling of the investigation usually results in a grand jury review. (Author abstract modified)