Part detective, scientist, engineer and law enforcement officer, the fire investigator represents the collusion of multiple careers rolled into one. It is the fire investigator who must explore, determine, and document the origin and cause of a fire or explosion. They must then establish what human actions were responsible for it, directly or indirectly.
Fire investigation is one of the most difficult of the forensic sciences to practice. In most forensic disciplines, even the basic question of whether a crime has been committed is normally obvious. During a fire investigation, an entire process must be undertaken just to determine if the case involves a criminal element or not. Arson investigators need to know not only basic science of fire behavior, but knowledge of many different areas of study (including construction, electricity, human behavior, etc.) Investigations, whether criminal or not, must follow a systematic approach applying sound and proven methods. A fire investigator must look at what is left behind after an incident and obtain information to piece together the events that occurred in the moments leading up to the event. After doing so, he must prepare a detailed report, and if necessary prepare a criminal case charging those responsible. In this scenario, the investigator will often file charges, make arrests, and assist the District Attorney in case presentation through their testimony.