New Concepts in Fire Investigation

An arson investigation that led to a possible wrongful conviction and subsequent execution in Texas highlights the important role science and technology play in fire investigations.

Cameron Willingham was convicted and executed of setting a house fire that killed three young children in 1991. Because DNA testing wasn’t commonly used on fire scenes in the 1990s, authorities relied solely upon the testimony of a lead investigator within the State Fire Marshal’s Office who concluded Willingham started the fire using an accelerant. Speculation still surrounds the case because a subsequent investigator said the cause should be reclassified as undetermined.

The means and methods by which fires are investigated have changed considerably in the 20 years since the Willingham fire, according to certified fire investigator Patrick Andler, of Andler & Associates, Inc. in Phoenix, Ariz.

Having investigated more than 4,000 fires during his career, Andler said his experience includes an arson homicide investigation that resulted in the release of Clarence David Hill, who was once on Arizona’s death row. Hill was convicted in the 1989 death of his landlord, but his conviction was overturned in 2005 based on DNA test results.

Findings Backed by Test Results

Fire investigation methods are based on procedures established by the National Fire Protection Association (NFPA). According to Andler, there is no other treaty or standard other than the NFPA guidelines, first published in 1992.

Fire investigation is complex and often leads to litigation, so science must support the cause of a fire. ‘The new concept of fire investigation is testing our hypothesis by going back and reconstructing the fire scene, by reconstructing the events occurring and conducting a full test by ignition,’ Andler said.

Because an entire fire scene is considered evidence, and spoliation is an important consideration, each scene requires an investigation to determine the ignition or fuel source, how the fire spread, and who may be responsible for causing the fire.

‘We’re finding that we must apply the scientific methodology on every fire scene,’ said Andler. ‘We cannot be selective. We must be able to show a competent ignition source, a competent fuel source, how the fire was able to communicate throughout a structure or vehicle — we refer to that as fire spread. And we also must be able to show responsibility.’

Currently, there are 80 recognized and validated standard fire patterns. Fire investigators, also known as cause and origin (C & O) experts in the property/casualty industry, interpret fire patterns in order to determine the origin of the fire.

New Tools of the Trade

One method Andler uses at his five-acre fire test laboratory in Phoenix is fire testing. ‘If we believe a fire started inside a microwave oven, we would get an exemplar microwave oven, test our hypothesis and test it to the stage of where we believe or don’t believe that the cause of the fire is related to that.’

Andler hosts an educational burn for property adjusters, attorneys, law enforcement personnel and risk managers every year. The fire investigation seminar is held at the five acre Forensic Fire Lab. ‘We have the capability of building a 16 foot by 20 foot room that we call our pad,’ Andler said.

Besides fire testing, investigators use several other methods at a fire scene.

A hydrocarbon detector and a canine detection dog — Andler’s is a three year old Labrador named Lightning Jack — can detect accelerants including gasoline, kerosene, or diesel fuel. The dog is certified as an accelerant detection dog. The results provided by the hydrocarbon detector and accelerant detection dog must be certified by a lab in order for the evidence to be admissible in court. Since accelerants deteriorate, it is important to use the methods at a fire scene as soon as possible. Per million (ppm)

Scan electron microscopes are a non-destructive tool used to discern material types and diagnose component failure. The microscopes can also help in establishing melting temperatures.

No longer used only in crime scenes, DNA testing is becoming a common fire investigation tool. ‘We’re using it a lot more than ever before,’ said Andler.

DNA, from the saliva on cigarettes to fingerprints on a gas can, can be sent to private labs located across the country for timely results. ‘We had a case where a cigarette butt was found at a fire seen. DNA was sent to a lab in San Diego…we can get results within 7-10 days,’ said Andler. ‘Public sector would take months because it isn’t a priority…’canines can detect amounts as small

Material experts like electrical engineers and metallurgists are critical during fire investigations. Metallurgists are helping determine whether a defective product is involved. In addition, they can determine melting temperatures of materials. Andler describes a criminal case he worked, State of Arizona v. Don Phillips, in which a fire investigator for the city testified that the temperature of the interior door handles were the same as the outside door handles. Andler’s metallurgist determined the door handles were not made of the same material, thus different melting temperatures applied.

According to Andler, the cases involving Willingham and Phillips highlight a lack of local and state resources that can affect fire official findings.

Electrical engineers utilize arc mapping in order to determine electrical arcs or faults that may have occurred during a fire. ‘By tracing out electrical circuitry in a building…and by using electrical engineers on a fire scene that helps us out,’ Andler said. ‘Takes a 5000 square foot room and narrows it down to 20 foot by 30 foot area.’

Fire vectoring and modeling are useful in mapping out the point of origin, showing how a fire initiated and in determining how quickly a fire spread. Andler and his team use colored tape from the point of origin through the rest of a house or building and create a slideshow or animation as a way to demonstrate the dynamics of a fire.

‘We’ll take a laptop on a fire scene and enter the thickness of sheetrock, the height of the ceiling, the windows, the carpeting, fuel load…enter it all into a computer and determine whether it was a fast or slow fire,’ he said. According to Andler, fire modeling assists fire investigators in determining fire spread and may reveal the point of origin.

Even photos obtained through Google Images are helpful in showing the condition of a building, the fuel load and type of roof structure prior to a fire. Surveillance tapes, cell phone cameras and GPS have also proven instrumental during fire investigations.