Fire Starter: Role of Forensics in Arson

By Georgios Christofidis, Ph.D.Reviewed by Sophia Coveney

Fire remains one of the major causes of mortality worldwide. In 1999, in the UK, 650 fire casualties were reported, while in the US, 7500 deaths per year are reported due to fire.

The majority of fire deaths occur at home and accident is the usual cause.  However, in 10% of cases, fire is a result of arson. Fire is also a common cause of mass disasters, involving a wide array of forensic issues, such as victim identification, determination of causes of death, reconstruction of the scene, investigation of the outbreak site and determination of the cause of the fire.

Besides the natural, industrial and traffic-related accidents, there are potential dangers of mass fire disasters in densely populated areas, as well as in amusement parks and hotels. Therefore, it is important that the forensic personnel dealing with fire crime scenes/accidents are well trained and can help facilitate the extraction of as much accurate information as possible from fire-related incidents.

Fire Investigation Principles and Training

Fire investigation has been scrutinized in the United States during the last decades, which has led to changes in what is expected of fire investigation, particularly in regard to the scientific basis for the examination of fire scenes and the academic qualifications of the forensic practitioners who perform the investigative work.

In the past, fire investigators were not always scientifically trained or qualified but rather developed their skills and theoretical knowledge in fire investigation by watching and gradually performing the activities experienced fire investigators did. However, from 1983 and onwards what would be the theoretical underpinning of fire investigation would be established. 

An analytical approach to fire scene investigation was presented in “Kirk’s Fire Investigation” in which the fire patterns were used to reach a conclusion with regard to the origin and cause of the fire. In 1992, the “Guide for Fire and Explosion Investigations” was published which merged the interpretation of fire patterns in one document and defined comprehensive standards of procedure for fire investigation.

Although the first scientific foundations of fire investigations had been set, Fire investigation was still one of a number of forensic disciplines that was seen as underdeveloped in the National Academy of Sciences report, “Strengthening Forensic Science in the United States: A Path Forward” which was published in 2009. Fire investigation has since then been shifting from an experience-based profession to more of a scientific one.

The utilization of scientific principles in fire scene examinations has resulted in an improvement in the reliability of fire origin and cause identification. There are now manuals and guidelines produced by various leading forensic technical groups for the investigation of fire scenes, multiple standards have been published for the range of scientific tests that are pertinent to fire investigation, such as the analysis of fire debris samples by gas chromatography, or the use of hydrocarbon sniffers to detect the presence of accelerants. Nowadays, forensic fire examiners are educated in collecting and analyzing samples from fire scenes along with general training in the science and dynamics of fire.

Scene Reconstruction of an Actual Case with the Help of Fire Forensics

A closer look at a specific alleged arson case which is about an amusement facility/hotel for adults in Japan will provide insight as to how beneficial fire forensics can be. Identification was completed by police investigation without difficulty owing to mostly intact bodies on the scene, supported by DNA analysis.

However, the fire-outbreak autopsy findings more or less pinpointed that the fire itself was not the cause of death. It appeared that the hot fumes which contained soot and toxic gasses were responsible for the deaths of 15 people. Traces of toluene and acetone were detected in all victims which also consolidates the assumption of copious smoke inhalation. There was no evidence of other injuries.

The study of pathological and toxicological findings of the victims demonstrated differences which provided hints of the location of the fire:  Victims found dead between the entrance and the alleged fire-outbreak site sustained severer burns with charring, while victims found dead in other areas did not have severe burns or had no burns at all.

Blood carboxyhemoglobin and cyanide levels showed tendencies towards different distributions among the victims. Blood carboxyhemoglobin levels were above 50% for all victims, demonstrating a correlation with cyanide levels for the blood located on the right part of the heart, but were higher for victims found around the suspected fire-outbreak site.

These observations also suggested how the survival rate in such a disaster could have been higher by using appropriate safety measures, such as smoke extraction, the availability of multiple escape routes as well as a fire alarm system to facilitate a swift escape from the building. So in this case, fire forensics were employed to successfully reconstruct a scene, identify the cause of deaths of the victims, pinpoint the fire-outbreak site while also highlighting the lack of anti-fire measures of the facility which led to the tragedy.

What is the Judicial and Overall Impact of Fire Forensics?

The results obtained when looking at the overall body of research indicate that forensic fire evidence may have an influence on the judicial outcomes of arson cases. Charges have been laid in a greater proportion of cases where forensic evidence provided support for the fire having been deliberately lit, and where ignitable liquid resources were detected.

An examination of the factors utilized by forensic fire examiners suggests that multiple factors are considered in reaching conclusions about the potential origin of a fire, and an important part of the decision-making process is the consideration of alternative hypotheses.

It has to be understood that fire forensics’ contribution to the criminal justice system is complex, and cannot be easily captured with broad metrics and case progression milestones. Instead, there is a need to consider how, and when, each piece of information is utilized in various ways by different actors in the system, including forensic scientists, investigators and legal decision-makers.

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