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Home > Investigations Division > Fire Investigation

Fire Investigation

"A fire or explosion investigation is a complex endeavor involving both art and science. The compilation of factual data, as well as an analysis of those facts, should be accomplished objectively and truthfully. The basic methodology of the fire investigation should rely on the use of a systematic approach and attention to all relevant details. The use of a systematic approach often will uncover new factual data for analysis, which may require previous conclusions to be reevaluated." - National Fire Prevention Association (NFPA) 921

The State of Maine has not adopted NFPA 921, but does use the code as a guide when investigating a fire or explosion scene. Investigating a fire scene is unlike any other investigation, in that most of the evidence one would otherwise think to look for has been involved in the fire, and possibly destroyed. But a trained professional knows what to look for when searching for evidence to support a finding of an accidental fire or an incendiary fire.

When stepping onto a possible scene of an incendiary fire, an investigator might begin by looking for obvious things such as cans or containers that look out of place, that could have been used to store accelerants. An investigator might also look for things in general that look out of place, such as a garage full of household furniture, when a fire destroyed an adjoining home void of furniture. As would be in the previous situation, an investigator must also look for the absence of things like furniture or valuables. If a person is committing a fraud arson, he or she will most likely remove all of the personal belongings that he doesn't want to lose forever in the fire.

A very important piece of evidence to look for at a fire scene is burn patterns. When a fire burns, it burns up and out, creating a V-pattern, with the bottom of the V being near the point of origin. If a fire scene contains more than one of these V-patterns, then the investigator must search to find a reason for this otherwise unnatural occurrence. Still, a fire is not automatically considered incendiary solely on the presence of numerous points of origin.

Once the point of origin has been determined, an investigator would then start to trace the spread of the fire throughout the scene. Many things can determine which way a fire goes. Normal fire spread dictates that a fire will spread in the path of least resistance, so open doors and windows are areas a fire will spread towards before spreading toward a closed door or window. And as before, because a fire spreads in the direction of an area that seems to not be the path of least resistance is not positively indicative of an incendiary fire. A door may be presently closed, but was not closed in the fire and so would now be the path of least resistance, but was not at the time the fire was burning.

A very useful tool that the State Fire Marshal's Office implements is the use of dogs to detect the presence of an accelerant material. There are two dogs in use in Maine: one is a black lab named Shasta and the other is a yellow lab named Huff. Dogs are trained to notify the investigator when he or she smells something like a hydrocarbon material. The dogs must be "worked" daily in order to be fed, and so the person taking care of the dog must set up a "scene" where there is some material for the dog to find. Once the dog has found the material and notified the investigator, then the dog will be given its dinner. Once a dog has indicated, a sample of the debris in that area can be taken and sent to the lab for examination and possible identification.

During an investigation, different types of evidence can be uncovered. There is the more obvious physical evidence, but also there is circumstantial evidence. Both types are extremely important, as a conviction for arson can be obtained from either type, or a combination of the two.

This is just a general summary of how an investigator might try to uncover the details of a fire. Interviewing witnesses and firefighters helps an investigator to determine why and how a fire occurred. There is much more involved in the investigation than is stated here, but this is an overview of what is involved.