Criminal investigator is a broad term that covers several professions in law enforcement. Criminal investigators include street detectives, crime scene investigators and laboratory specialists.
Perhaps the most visible of the various professions within the category of criminal investigator is the police detective. Police detectives follow up on information on crimes. Detectives interview witnesses, follow up on leads, develop relationships with informants and write reports on the progress of cases that they may work on for many years. Most detectives start out as police officers and are promoted into the detective position.
Crime Scene Investigator
Although lumped together as crime scene investigators (CSI), the people who examine crime scenes have distinct specialties, from forensic photography to fingerprinting. Crime Scene Investigator Network says that people interested in a career as a CSI should get a college degree. Specific areas of study would depend on the needs of departments in the location where the person wants to work, but general photography and computer skills are almost universally required.
Laboratory specialists are criminal investigators who focus on analyzing trace evidence. These are the people who identify whether a bullet has been fired from a specific gun, whether partial fingerprints match prints stored in national databases, and whether fibers from a suspect's clothing match those found at a crime scene. LegalCriminalJusticeSchools.com indicates chemistry is the best degree in preparation for becoming a laboratory specialist.
Computer Crimes Investigator
Most law enforcement agencies employ investigators who specialize in the investigation of computer crimes. The Federal Bureau of Investigation, for example, has four areas of crime that computer investigators focus on. Their computer crime investigators try to stop people who spread computer viruses, identify and apprehend Internet child pornographers, investigate people acting contrary to national security and investigate Internet fraud.
International Crime Investigator
The Institute for International Criminal Investigations is a school dedicated to teaching people the skills necessary to investigate war crimes, genocide and crimes against humanity. People with the type of training provided by the Institute are hired by the United Nations and sent to locations around the world to investigate potential violations of international law. These investigators may have to document violations with photography, talk to witnesses in the field and make their reports all while traveling in a war zone.