Mr. And Mrs. Nash” owned a $400,000 home at the foot of a mountain near Boulder, Co. It was a very nice property including a nearby ‘Mother-In-Law” guesthouse.

Mr. and Mrs. Nash asked their friend and coworker Lisa to house-sit, while the Nashes left for a European vacation. Lisa invited her friend Paula to stay for the weekend. On Friday night, Paula was given the master bedroom, and Lisa took one of the twin beds in the spare room. Lisa chose not turn on the electric baseboard heat: instead, she opted for the warmth of the electric blanket already on the bed.

At 3 AM, Lisa’s feet were uncomfortably warm. She woke up and discovered why: the foot of her bed was in flames.

Lisa ran from the bedroom, screaming to wake Paula. When Lisa returned to the bedroom, the bed was fully in flames.

Lisa and Paula looked for water; couldn’t find a bucket. Eventually they were able to bring water from the hot tub across the hall, but it was too late… the room was engulfed in high flames and lots of smoke.

Lisa and Paula ran to the 'Mother-In-Law' guesthouse, and called the fire department.

Several days later, Anderson Engineering was brought into the case to determine the cause of the fire.


The initial contact in our line of work usually comes from an insurance company, attorney, or fire investigator.

In this case, we received a call from an attorney representing the insurance company holding Mr. and Mrs. Nash’s homeowner’s insurance policy.

Their insurance company had paid the Nashes their claim, but was determined to recoup their loss. The Fire Investigator who examined the scene pointed to the electric blanket as the probable source of the fire.


This case is somewhat unusual because the fire scene investigation was done prior to Anderson Engineering’s involvement. Very often Anderson Engineering examines the actual fire scene in the course of their work.

During the actual firefighting, the fire department cleared out everything from the room of fire origin, including the beds, dressers and chairs. These were thrown into the yard out the bedroom window. (Firefighters are trained to make sure there are no lingering embers, so there is no chance of rekindling a fire. Keeping the forensic evidence intact is not always a top priority.)

During the investigative portion of this case, Anderson Engineering relied on a review of the Fire Investigator’s report, a photographic reconstruction of the scene, a critical assessment of the fire’s burn patterns shown in the photographs, first-hand eyewitness accounts, and an inspection of the artifacts from the fire.

Part of the forensic electrical engineer’s job in a case like this is to determine how electrical power is fed into the room of origin. The engineer needs to discover what other appliances were in the room, and whether or not they were energized at the time of the Fire Reconstruction. The reconstruction of this fire scene was accomplished largely through photographs and statements taken from the homeowners and eyewitnesses.

Artifacts and other debris from the fire were also provided to Anderson Engineering. A scant pile of burnt remains from two electric blankets would provide the key forensic evidence in the case – but not before a determination of cause and origin was made.


In determining the cause and origin of a fire, the first thing to be determined is Origin. You cannot determine Cause without first determining Origin. (Specialists engaged in this kind of work would rather call it “Origin and Cause.”)

In this case, the Origin was determined through fire scene reconstruction, a study of the burn patterns and of eyewitness testimony.

(With regard to a fire’s origin, it should be said here that the Fire Investigator’s report is not always gospel. When Anderson Engineering is asked to determine the cause of a fire, part of Anderson’s determination is based on whether or not they agree with the evidence cited in the Fire Investigator’s report. In this case, however, Anderson was satisfied that the electric blanket caused the fire.)


Remember: Only when you have determined Origin can you begin to determine Cause.

In this case, the cause of the fire was determined by: investigating for other potential ignition sources in the area of origin and ruling out any other potential ignition sources (in this case, things like careless smoking or intentional incendiary materials that might indicate arson). In this case, there were no candles in the room, no smoking had taken place in the room, and Anderson Engineering determined that the most likely cause of the fire was the electric blanket.

Easy to say. Hard to prove. It is up to a careful reading of the forensic evidence - in this case, a dubious pile of burnt electric blanket remains – to prove the claim.

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