Fire Investigator
Chapter 14: Physical Evidence
Ready for Review
· At a fire scene, the entire scene, including the fire patterns, sources of ignition, security and fire detection equipment, and items associated with the cause of the fire, is considered physical evidence.
· The fire investigator is responsible for locating the evidence, properly identifying the evidence, collecting the evidence, documenting the evidence, examining and storing the evidence, and arranging for testing of physical evidence from a fire or explosion scene.
· Common physical evidence at a fire scene may include traces of ignitible liquid in flooring, a tool mark that is at a point of forcible entry or that indicates adjustment of a critical valve, a faulted electrical circuit, fingerprints, blood, or other physical item or mark that helps the investigator establish fact.
· Although the most important physical evidence in a fire investigation is generally found within the area of origin, important evidence can also be found elsewhere within the fire scene and frequently outside the fire scene as well.
· Opportunities to contaminate evidence occur during firefighting, overhaul and salvage operations, evidence handling, storage, and transportation.
· The collection of physical evidence is governed by the type, form, size, and condition of the evidence.
· Collection methods for physical evidence depend on the following factors:
· Physical state
· Physical characteristics
· Fragility
· Volatility
· The first stage in identifying collected physical evidence is photographing the evidence where it was found and placing the evidence into a scene drawing by measuring its exact position from fixed objects such as walls or door casings.
· Crime scene procedure calls for marking, tagging, or bagging of evidence. It is best to mark directly on the evidence itself if this will not be destructive.
· After an item of evidence has been collected, it may be submitted for examination or testing. Testing is often performed to establish chemical composition or for failure analysis.
· The major concern when transporting physical evidence for storage or testing is maintaining the physical integrity of the evidence.
· Forensic and legal requirements mandate that evidence be positively identified and maintained in a chain of custody from the point where the evidence is collected right to the courtroom.
· Many factors influence the length of storage for physical evidence, including the possibility of criminal and/or civil trial.