This article describes the basic steps to be followed in carrying out a fire investigation. Fire investigators need to understand why they have been asked to investigate a particular fire. They need to approach the fire with an open mind, and a presumption that the fire, like most fires, was the result of an accident. The investigation needs to be carefully planned, and safety of the investigator is of prime importance. The scene must be documented, reconstructed, and documented again before a credible origin hypothesis can be put forward. Origin determination is difficult and error prone. Artifacts that tend to validate an origin hypothesis include finding evidence of electrical damage near the origin, and ultimately identifying a cause within that area. During the processing of the scene, investigators need to be mindful of the fact that other parties may have an interest in viewing the evidence. Care should be taken in documenting and collecting any evidence removed from the scene. Finally, a general reporting procedure, compliant with ASTM E 620 that is the Standard Practice for Reporting Opinions of Technical Experts, is described. Keywords: inspection; documentation; reconstruction; spoliation; fire scene; scientific method; documentation; spoliation; presumption; NFPA 921
