The Evolution of Fire Investigations into the 21st Century

Criminal Investigations: Fires and Explosives

The forensic sciences have benefited greatly from innovations in computer technologies and even decades-old “cold case” crimes are now being routinely solved as a result. In particular, computer fire models have become increasingly sophisticated in their ability to identify the source, causes and timing of fires. Likewise, forensic investigations of terrorist uses of improvised explosive devices (IEDs) have benefited from a growing body of knowledge concerning their design, construction and deployment as well as the fragmentation of pipe bombs with varying case thicknesses. To determine their status of these forensic methods, the purpose of this paper is to provide a discussion concerning the evolution of fire investigations and their impact on arson cases and the reliability of computer fire models at trial. In addition, an overview of terrorist use of IEDs and what is known about the fragmentation of pipe bombs with varying case thicknesses is followed by a summary of the research and important findings concerning these forensic methods in the conclusion.

The evolution of fire investigations and its impact on arson cases and the reliability of computer fire models at trial

The evolution of fire investigations over the past 30 years or so has changed the nature of the enterprise from one in which suppositions and long-held beliefs by investigators has been replaced with a model that emphasizes scientific analyses (Lentini, 2012). Moreover, in the past, the majority of fire investigators received no formal training and relied instead on “the belief systems of superiors” and their empirical observations based on their individual experiences in investigating fires (Lentini, 2012, p. 37). Although significant progress has been made in modernizing fire investigations, the profession is still marred by a lack of needed funding to ensure that practitioners possess the skill set that is needed to perform scientific fire investigations and to allow them to keep pace with new developments in the field (Lentini, 2012).

Notwithstanding these constraints, the United States has succeeded in developing national standards for the professional qualifications for both public and private fire investigators. Besides remaining current with new developments in the field and pursuing continuing education as in other professional fields, the National Fire Protection Association’s certification as a professional fire investigator now requires a minimum of current knowledge at an advanced educational level for the following:

(1) Fire science;

(2) Fire chemistry;

(3) Thermodynamics;

(4) Thermometry;

(5) Fire dynamics;

(6) Explosion dynamics;

(7) Computer fire modeling;

(8) Fire investigation;

(9) Fire analysis;

(10) Fire investigation methodology;

(11) Fire investigation technology;

(12) Hazardous materials; and

(13) Failure analysis and analytical tools (Lentini, 2012, p. 48).

Taken together, it is clear that modern fire investigations draw on a wide range of disciplines, fields and sciences that reflect their ongoing evolution. In addition, fire investigators today can also benefit from education and training in the primary motivators for criminally set fires which can help them determine the cause of fires but whether it was intentionally set in the first place. For instance, according to Pavlisin et al. (2009), fire investigators for insurance companies now search for any evidence of criminal intent during their initial investigations which can help identify the arsonist. In this regard, Pavlisin et al. (2009) report that, “The initial fire investigation may yield one or more ‘red flags’ that require the insured to be ruled out as having intentionally set the fire” (p. 408). Although every fire investigation is unique, some typical “red flags” of most interest to fire investigators include: unexplained fire findings; suspicious burn patterns; suspicious origins or causes of the fire; inconsistencies in explanations or alibis of suspects (including the insured); and financial problems that are being experienced by the insured that might motivate a fire insurance claim. In addition, recent removals of pets or guard animals or items that are especially valuable or have sentimental value are also regarded as “red flags” that warrant follow-up investigation (Pavlisin et al., 2009).

The evolution of fire investigations has also been characterized by the increased use of a wide array of computer-based analytical techniques, including thermal analyses, elemental chemical analyses, mass spectrometry, chromatographic methods, and the isolation of compounds from fire debris (Paál et al., 2022). Likewise, fire investigators now have access to a growing database of previous research into how fire behaves in numerous settings. Nevertheless, the vagaries of fire and its effects has made computer modeling especially challenging. As noted above, expertise in the computer modeling of fires is now a requirement for professional certification of fire investigators, but the lack of consistent reliability of the findings that emerge from computer models are still not admissible as evidence in courts (Gabbert, 2010).

Overview of terrorist use of improvised explosive devices (IEDs), such as pipe bombs and what is known about the fragmentation of pipe bombs with varying case thickness

The latter half of the 20th century made it clear that multiple asymmetric warfare strategies were highly effective in combating a larger and stronger foe. Despite efforts on the part of the U.S. military and intelligence authorities, the use of IEDs by terrorist organizations continues to accelerate in certain regions of the world, including those beyond the Middle East (Drozl et al., 2018). Moreover, many analysts also caution that existing strategies to detect and protect troops and materiel from IEDs is severely lacking (Drozl et al., 2018). Nonetheless, the vast majority of the incidents that the U.S. military has with IEDs has been gathered from conflicts in the Middle East in recent years. In this regard, Barker (2011) reports that, “Homemade bombs or improvised explosive devices are staple weapons of conflicts in South Asia and especially Southern Afghanistan and Western Pakistan, where the Taliban, their affiliates, and other armed groups use them to undermine recognized governments and policies” (p. 600).

Although the Taliban’s takeover in Afghanistan in mid-2021 cannot be entirely attributed to the use of IEDs, it is clear that these deadly devices played an important role in hastening the process. More troubling still, terrorist organizations have developed improved skills in constructing IEDs and they have become even deadlier than in the past (Barker, 2011). Indeed, the “improvised” part of their designation should not mislead observers into thinking all of these devices are of amateurish design, and terrorist organizations consistently devote significant resources into developing even more lethal devices (Barker, 2011). In fact, the U.S.-led international coalition in the Middle East suffered literally thousands of these attacks over the years, and their use is expected to continue to grow in popularity as terrorist groups of all ilk gain even more experience in their design and deployment (Barker, 2011). In addition, there have also been instances of the use of pipe bombs by domestic terrorists in the United States in recent months. For instance, according to Walsh (2021), the Federal Bureau of Investigation (FBI) released videotapes of an individual leaving pipe bombs outside the Republican and Democratic national committee headquarters in Washington, D.C. the day before rioters stormed the U.S. Capitol. Both of these devices were described by the FBI as “viable” and capable of causing “serious injury or death” (as cited in Walsh, 2021).

While explosive-laden vehicles have also been used in recent years (Drozl et al., 2018), pipe bombs remain the most popular types of IEDs used by terrorist organizations today (da Silva et al., 2020). In this regard, da Silva et al. (2020) emphasize that, “Among all the improvised explosive devices known, pipe bombs are one of the most popular devices used by terrorists. They are simple to use, easy to construct and materials are readily available” (p. 306). Because fragmentation of pipe bomb cases represents the main mechanism for inflicting human casualties, the thicknesses of the pipes that are used has a direct effect on their lethality (de Silva et al., 2020). While additional research is needed, the studies to date confirm a direct correlation between case thickness and the size and velocity of detonated pipe bomb fragments (da Silva et al., 2020).