Crime scene investigators (CSIs) are some of the first members of law enforcement to respond to the scene of a crime. There they collect and preserve evidence, document the scene, and take all items recovered back to the forensic lab for processing and examination. They work at all levels of criminal investigation, from small-town police departments to federal law enforcement agencies.
Local Police Departments
Many towns and cities, especially densely populated or major metropolitan areas, have a dedicated staff of crime scene investigators. The larger the city and the department, the more crime scene investigators they employ. In very small towns or rural areas, police officers sometimes double as crime scene investigators. Some local police departments hire civilian CSIs, but most are sworn police officers. They typically have an associate's or bachelor’s degree in criminal justice or forensic investigation, or have completed police academy training.
State Law Enforcement Agencies
At the state level, law enforcement agencies typically employ a large staff of crime scene investigators. State law enforcement agencies, typically referred to as the state’s bureau of investigation, often handle more challenging cases, such as cold cases or those in rural areas where the local police department lacks the resources to properly investigate the crime. Because of this, a state law enforcement agency must have a sufficient staff of CSIs to respond to the dozens of cases the bureau handles at a given time all across the state. State agencies are more likely than local departments to require at least an undergraduate degree, with some preferring graduate-level training.
Many federal law enforcement agencies operate their own teams of crime scene investigators. Similar to agencies at the state level, federal bureaus often respond when additional resources are required, so their CSIs frequently have advanced training and might specialize in a single area of crime scene analysis. The FBI, for example, has both an evidence response unit and a crime scene documentation unit. In addition, some CSIs employed by the FBI specialize in recovering evidence from underwater crime scenes or using scent dogs to identify and track down clues or suspects.
All branches of the military operate forensic investigation units, which include crime scene investigators. Some work in the battlefield, where they investigate attacks on soldiers and other potential terrorism-related incidents. They also respond to crime scenes located on military bases in the United States and abroad. Like CSIs employed by police departments, they dust for prints, collect evidence and document the scene. They also consult with state and local law enforcement agencies and testify in civilian trials or those held in international courts. Some are civilians, though many are members of the military.