A criminalist is someone who specializes in the examination and analysis of physical evidence in order to assist law enforcement agencies in solving crimes. There are several other terms that are often used interchangeably with criminalist. Forensic scientist, for instance, denotes someone who applies scientific methods to the investigation of a crime scene. Medical examiner refers to someone who determines the cause of death by conducting an autopsy. A crime scene investigator collects and photographs evidence from a crime scene. A ballistics expert determines the origin and trajectory of bullets fired during a crime. A serologist examines bodily fluids like blood to determine the presence of DNA. All of these professionals, and more, are essential for the successful resolution of a criminal case.