Not all forensic scientists are criminalists, but all criminalists are forensic scientists. The oldest forensic science laboratory in the United States was created in 1923 in Los Angeles, California. When the FBI organized a national laboratory for forensic science in 1932, it was the first centralized way to offer a variety of forensic services to law enforcement agencies around the country. It is now the world's largest forensic lab, and its structure serves as a model for state and local laboratories. In 1981, the FBI opened the Forensic Science and Research Training Center, which was dedicated to developing new technologies and to training crime lab personnel.
Crime labs operate at federal, state, county and municipal levels.
There is no single model that represents them all, in part because of budget restrictions for purchasing equipment and hiring personnel. Most are affiliated with police departments, some are under the direction of the district attorney or the coroner, and universities oversee a few. In any given lab, there may be one lone technician or over one hundred. A full service crime lab for a large city would include an evidence collection unit that is trained in what to look for and how to collect and preserve evidence to avoid corruption. Most trace evidence, such as glass fragments, soil, explosives, non-natural fibers, and paint are analyzed here.