Fire Debris Analysis

By Eric Stauffer, Julia A. Dolan and Reta Newman

The study of fire debris analysis is vital to the function of all fire investigations, and, as such, Fire Debris Analysis is an essential resource for fire investigators. The present methods of analysis include the use of gas chromatography and gas chromatography-mass spectrometry, techniques which are well established and used by crime laboratories throughout the world. However, despite their universality, this is the first comprehensive resource that addresses their application to fire debris analysis.

Fire Debris Analysis covers topics such as the physics and chemistry of fire and liquid fuels, the interpretation of data obtained from fire debris, and the future of the subject. Its cutting-edge material and experienced author team distinguishes this book as a quality reference that should be on the shelves of all crime laboratories.

• Serves as a comprehensive guide to the science of fire debris analysis
• Presents both basic and advanced concepts in an easily readable, logical sequence
• Includes a full-color insert with figures that illustrate key concepts discussed in the text

• Language: English
• Publisher: Academic Press
• Release date: Dec 10, 2007
• ISBN: 9780080556260

Eric Stauffer

Eric Stauffer is a criminalist presently living in Switzerland. In 1998 he obtained his Master-equivalent degree in forensic sciences from the Institut de Police Scientifique et de Criminologie at the University of Lausanne in Switzerland. In 1999 he moved to the United States and, two years later, obtained another Master’s degree in forensic sciences from Florida International University in Miami, Florida. Mr. Stauffer is certified as a Diplomate and a Fellow of the American Board of Criminalistics, with a specialty in the area of fire debris analysis. He is also a Certified Fire and Explosion Investigator (CFEI) and a Certified Fire Investigation Instructor (CFII) both from the National Association of Fire Investigators (NAFI). During his early career as a criminalist, Mr. Stauffer worked as a crime scene officer and a firearms and toolmarks examiner. In 2001, he moved to Atlanta and joined the private sector as a fire investigator and fire debris analyst. As such, his duties involved the investigation of numerous residential, commercial, and vehicle fire scenes to determine their origin and cause and, at the laboratory, the examination of fire debris samples for ignitable liquid residues. In 2006, he moved back to Switzerland to conduct research in forensic sciences, notably in fingermark enhancement techniques and fire investigation. He is currently pursuing doctoral studies at the School of Criminal Sciences at the University of Lausanne. From 2003 to 2006, Mr. Stauffer was Chair of the Fire Laboratory Standards and Protocols committee of the Scientific Working Group on Fire and Explosives (SWGFEX). He also served as a subject matter expert for the development of the fire debris validation kit produced by the National Forensic Science Technology Center (NFSTC). Mr. Stauffer is a recognized speaker and instructor in the field of forensic sciences and, more particularly, in fire investigation and fire debris analysis.

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PhD

Introduction

The journey of a thousand miles begins with a single step.

Lao Tzu, Chinese philosopher (604 BC-531 BC)

1.1 THE OTHER USE OF GASOLINE AND DIESEL FUEL

For a small single story building, the prescription is two incendiary devices each using 5 gallons of accelerant. […] It is usually unnecessary and a waste of precious time to gather up flammable materials at the scene (e.g. fenceposts, branches, wooden furniture). It is much more valuable to bring more fuel if you are concerned about the success of your fire. Gasoline and diesel are perfectly suited to delivering large quantities of heat, not too fast and not too slow.

These lines, found in the 2001 publication of the Earth Liberation Front entitled, Setting fires with electrical timers, summarize relatively well why ignitable liquids often are used as accelerants in committing arson [1]. Fortunately, the average layperson does not comprehend the chemistry and physics of fire and, more particularly, the use of ignitable liquids as accelerants. Thus, it is frequent that a criminal willing to set a structure (building) or a vehicle on fire douses it with an incredibly large amount of gasoline. Although this practice is highly inefficient from a combustion perspective, the resulting fire scene may contain a great amount of gasoline residues—an advantageous situation from a forensic perspective—which can be detected by the fire investigator with the help of the crime laboratory. The identification of ignitable liquid residues (ILR) from fire debris samples collected at a fire scene constitutes the practice of fire debris analysis.

Gasoline was not developed for intentional use by arsonists. As a matter of fact, it was developed in the early 1800s to fight against lice and their eggs pharmaceutically. However, this use was discontinued when it was discovered that gasoline was carcinogenic and led to a greater risk of dermatitis. Additionally, its use against lice usually was not carried out in a very safe manner from a fire safety perspective, which led to serious injuries and deaths [2]. In 1855, Benjamin Silliman Jr. (New Haven, Connecticut, USA) patented the distillation of crude oil into a number of products, including gasoline [3]. As the car industry expanded, gasoline underwent a significant evolution to become the fuel of choice for automotive vehicles. In 1919, gasoline became the most commonly produced petroleum-based product in the United States. In 2006, more than three billion barrels were produced in the United States [4].¹

Gasoline is one of the accelerants of choice for arsonists. Actually, it is the most commonly encountered accelerant in probably every country around the world. The reasons lie in the fact that it is readily available, inexpensive, easy to transport, and more importantly, it is easy to ignite and it provides the necessary energy to accelerate a fire. Arsonists do not travel great distances to find the perfect accelerant; they use whatever works. Although gasoline is the most used accelerant, it is clear that many other ignitable liquids also are used to start fires, such as charcoal lighter fluids, paint thinners, lamp oils, diesel fuels, alcohols, and many other solvents.

Arson v. Incendiary, Intentional, or Deliberate Fire

The term arson—from the medieval Latin term arsio, which comes from the Latin verb ardere (to burn)—is a legal term in many countries. Thus, its exact definition varies from one jurisdiction to another. However, a general definition commonly accepted for arson is a criminal act of deliberately setting fire to a property. Arson implies that there is criminal intent and deliberate burning of some object, usually a structure or a vehicle. In some instances, the terms intentional fire, incendiary fire, or deliberate fire are used interchangeably with arson. These terms are used in order to avoid citing the term arson, which would imply a legal meaning. Setting some dead leaves on fire in the backyard (respecting the jurisdiction’s regulations) or lighting a grill to cook some meat are two examples of fires intentionally started. However, typically these are not labeled arson as they do not include a criminal element. Indeed, when the term intentional fire is used, the criminal intent of the fire often is implied, even if not directly stated. Thus, when statistics present intentional or deliberate fires rather than simply arson, one should consider that they include only fires that have a criminal connotation.

Nevertheless, some jurisdictions prosecute fires that have been accidentally set by a human being. Thus, although these fires are part of a criminal prosecution, they typically do not involve a criminal intent and are not classified as part of the intentional fires nor as part of arson. Throughout this book, the terms arson, deliberate, intentional, and incendiary fires are used interchangeably unless otherwise stated.

Unfortunately, arson is a problem that goes much beyond property crime. It also takes the lives of many people and animals every year, it produces feelings of insecurity to citizens, and it costs enormous amounts of money in damages, victim’s compensation, government services (firefighting, law enforcement, government insurance, etc.), and private insurance services. Nevertheless, it is a crime difficult to prosecute because, by its very nature, it destroys evidence. In the United States, though relatively accessible, statistics in fire and arson investigation are not very accurate and one must be very prudent when interpreting the figures provided. One of the main reasons for such precaution is that the reporting system is based on fire department reports rather than fire investigation reports [5]. Thus, the fire chief responding to the scene may declare a fire electrical without having been trained to investigate fire. The scene might later reveal that the fire was incendiary when subsequently investigated by the fire marshal or a private fire investigator. Furthermore, there is a significant number of fires for which the exact cause remains unknown. The field of fire investigation is very prone to differences of opinion. Thus it is never truly known what caused some fires even after thorough investigation. Finally, though general statistics about fires are readily available (numbers, locations, types, etc.), specific data regarding the use of ignitable liquids or the types of ignitable liquid used in criminal fires is not readily available.

Accelerant v. Ignitable Liquid

The term accelerant is often wrongfully used synonymously with ignitable liquid. It is important to remember that a material is defined as an ignitable liquid based upon its physical and chemical properties, but a material is defined as an accelerant based upon how it is used. An accelerant is [10]: a fuel (usually a flammable liquid) that is used to initiate or increase the intensity or speed of spread of fire. Therefore, not all flammable liquids found at a fire scene are accelerants and conversely, not all accelerants used to commit arson are liquids. A paper trail used by an arsonist to set a house on fire is an accelerant. However, the presence of gasoline on a piece of carpet placed in a garage under vehicles to collect oil stains is not an accelerant; rather, it is defined as an incidental liquid present on the substrate.

As an example, a criminalist in the laboratory receives two liquid samples from an investigator: A and B. Following analysis, both samples are identified as gasoline. At that point, the scientist can state with no further information that both samples A and B are ignitable liquids. The investigator, knowing the sources of the liquids, can infer whether or not they are accelerants. Sharing the information that sample A was retrieved from the gasoline tank of the suspect’s lawnmower, and that sample B was recovered from glass bottle fragments with a wick protruding from the neck portion found at a fire scene, the investigator can infer whether they were used as accelerants or not. Sample B was used for the purpose of initiating a fire; therefore, it is an accelerant. Conversely, sample A simply was used as a fuel for an internal combustion engine, and is therefore not an accelerant. Both samples are ignitable liquids and have the same chemical composition, yet one is an accelerant, and the other is not. It is crucial that the criminalist not refer to ignitable liquids as accelerants based solely on their chemical and physical properties. The term accelerant necessarily refers to the context of the fire and the investigation. This is why, throughout this text, the terms ignitable liquids and ignitable liquid residues usually are used; only under the rare and appropriate circumstances, do the authors refer to accelerants.

In spite of this, it is always interesting to look at some of these numbers and to have a rough, even if knowingly inaccurate, idea of the proportion of different factors surrounding fire and arson investigation and, more particularly, the use of ignitable liquids at fire scenes. In 2005, Hall reported that less than 10% of the intentionally set structure fires involved the use of incendiary devices [6]. Table 1-1 presents some data extracted from an older report including US home fires that occurred between 1994 and 1998 (average annual values are reported) [7]. It shows the breakdown of different classes of ignitable liquids and their use in intentional or suspicious fires. As previously stated, gasoline is the most frequently encountered accelerant used in arson cases, followed by light flammable liquids, which are usually the most readily available and efficient products.

Table 1-1 The different types of ignitable liquids found at fire scenes in a study carried out in the United States between 1994 and 1998 [7]. Values are provided as annual average number of fires. The last column is the proportion of fires that are either intentional or suspicious in nature for each category of liquid. This means that 52.6% of the fires where gasoline is found are intentional or suspicious in nature. Note that the categories used in this table do not correspond to the ignitable categories commonly used in fire investigation and forensic sciences.

Again, these figures must be cautiously interpreted, as there was an annual average of 80,000 structure fires that were caused by arson during this period and fewer than 4,000 arson cases were reported to involve the use of ignitable liquids [8]. In practice, it seems that the proportion of arson fires involving the use of ignitable liquids as accelerants is much higher than the 5% value reported. As a matter of fact, statistics provided by the Office of the Ontario Fire Marshal show that approximately 10% of the 4,985 fires investigated by that agency between 1995 and 2005 involved an ignitable liquid as the first material ignited [9]. Also note the fact that this agency is likely to handle a greater proportion of intentional/suspicious fires than a regular fire department, thus there is a higher proportion of fires involving an ignitable liquid.

1.2 FIRE INVESTIGATION

1.2.1 Principle

Whenever a fire occurs, an investigation almost always ensues. Depending on the laws in place within the jurisdiction, parties responsible for the fire are prosecuted under penal law if the fire was set intentionally or even, in some instances, if the fire was set accidentally. All the forensic sciences have goals of determining if a crime has been committed, identifying its victim(s) and perpetrator(s), and identifying the modus operandi of the perpetrator(s) [11]. Fire scene investigation, also referred to origin and cause investigation, is a specialized discipline of forensic sciences, it is carried out mainly to answer the question of whether or not a crime has been committed and what the modus operandi of the perpetrator is.² The identification of victim(s) and perpetrator(s) is usually performed using a traditional criminalistic approach and does not concern the origin and cause investigation itself.³ Therefore, the goals of fire scene investigation are to answer the following two specific questions: Where did the fire start? and Why did the fire start?

A/ Origin of the Fire

The first question refers to the determination of the origin of the fire. The fire investigator must identify the first material ignited and its location, which is called the point of origin (or the seat of fire). It is critical to identify the point or area of origin because without it, it is impossible, except under some particular circumstances, to answer the second question. When it is not possible to identify an area of origin or a very precise point, the subsequent process is thus greatly complicated.

B/ Cause of the Fire

The second question refers to the determination of the cause of the fire. The fire investigator must identify the ignition source that ignited the combustible which first caught fire, and the circumstances that brought the two together. The ignition source is found at the point of origin unless it has been subsequently removed. In order to determine which possible sources of ignition are present and which ones are suitable to ignite the surrounding combustible, it is essential for the investigator to be aware of the different sources of thermal energy, their transfer, and the properties of the materials available in the area of origin.

1.2.2 Investigative Agencies and Investigators

In most countries, it is the responsibility of the police department to determine if a crime (arson) has been committed or if a fire was accidental or resulted from negligence. The fire department is usually the first entity to arrive at the scene to carry out rescue and extinguishment activities. Once these operations terminated the responsibility of the scene is transferred to the investigative authority. In the United States as well as in some other countries, such as England and Australia, fire departments are given the legal authority to conduct fire (and explosion) scene examinations and to proceed with a complete criminal investigation. Such departments usually have sworn law enforcement officers carrying weapons who are responsible for conducting the investigation. Even though they are not part of the police department per se, they can fulfill all the functions of a police detective. In other countries, the investigation of fires and explosions is mostly the responsibility of the police department, which may have specialized units dedicated to that duty.

Although origin and cause investigation is a specialized discipline of forensic sciences, many fire investigators are not forensic scientists and did not undergo specific forensic training. This is particularly true in jurisdictions where fires and explosions are investigated by fire departments such as in the United States. Thus, their approach to the examination of the fire scene is purely from a fire perspective, which consists in determining the origin and the cause of the fire. In this fashion, they may not always investigate a fire scene with a comprehensive criminalistic approach and may not answer the other main goals of forensic sciences, namely, identifying the victim(s) and perpetrator(s). This might also be one of the reasons why arson crimes do not present a significant rate of clearance.

1.2.3 Investigation Steps

Figure 1-1 shows the typical steps of a fire investigation. The investigation of a fire starts with the occurrence of a fire or an attempted fire. In general, the fire department is called first to proceed to the extinguishment and other rescue operations. It is important for the investigator to be aware of the fire department intervention so he or she can evaluate the modifications brought to the scene through the action of the firefighters. At some point, the investigator is summoned to the scene. He or she may arrive during the extinguishment operation or at a later time.

FIGURE 1-1 The different steps of a typical fire investigation.

Before the investigator actually starts the examination of the scene, it is crucial to gather as much background information as possible regarding the fire. Background information includes interviews of victim(s) and witness(es), owner(s) of the premises, and collection of information from the fire department, police department, and other official entities. Fire departments usually prepare a run report of the intervention, which contains a limited amount of information. It is also crucial for the investigator to interview firefighters as well as the chief in charge. The ultimate goal of the collection of background information is to establish the most detailed account of the circumstances surrounding the fire, most importantly the chronology of the different events preceding the fire.

Then, the observation of the scene begins. The scene is examined from general to particular and from the least burned area to the most burned area. First, the investigator goes around the scene to comprehend the extent of the fire. Then, the investigator observes fire and smoke patterns in order to identify the origin of the fire. Once an area of origin is determined, the investigator proceeds to the identification of all ignition sources within that area and determines the potential causes of the fire.

At any time during the observation of the scene, the investigator may call other specialists to assist in the investigation. These specialists can be forensic scientists or other individuals with particular skills and knowledge relevant to the investigation. These include engineers, chemists, electricians, mechanics, and the like.

Also, during the investigation, different items of evidence usually are collected. One of the very commonly collected items of evidence is a fire debris sample in order to determine the presence of ignitable liquid residues. Other types of evidence may also be collected such as electrical wiring, remnants of a timing device, mechanical parts, and such.

Next, the evidence is forwarded to the laboratory for examination. The investigator should personally contact the criminalist(s) performing the examination of the evidence to communicate information regarding the circumstances of the fire and the evidence and to ensure that the most pertinent examinations are conducted. Also, in some instances, the forensic scientist may request additional items of evidence.

During the scene investigation, the investigator usually develops a hypothesis or a series of hypotheses regarding the origin and cause of the fire. Information provided by specialists at the scene and results from the crime laboratory are integrated into this process. These hypotheses are then tested using the scientific method and are refined as necessary. The goal is to validate the hypothesis in order to reach a conclusion. At that point, the investigator may want to gather more information pertinent to the case. Additionally, testing might be necessary to determine if a hypothesis is valid or not.

Finally, once the investigation is complete and the most suitable hypothesis validated, it is possible to reach a conclusion and write a fire investigation report. The four possible conclusions—from a legal perspective—with respect to the cause of a fire are deliberate, accidental, natural, or undetermined. The proportion of undetermined fires is actually quite significant, due to the destructive nature of fire.

1.3 WHAT IS FIRE DEBRIS ANALYSIS?

1.3.1 Definition

Fire debris analysis (FDA) is the science related to the examination of fire debris samples performed to detect and identify ignitable liquid residues (ILR). When fire debris samples suspected to contain traces of ignitable liquid are collected from the fire scene, they are forwarded to the crime laboratory along with the request to identify the presence of any possible ILR.

For most criminalists, the analysis of fire debris samples starts at the laboratory when the sample is brought in by the scene investigator. However, the story of the sample begins much earlier. Its history actually starts at the moment when the materials constituting the sample are produced and assembled together. Then, it undergoes fire (possibly preceded by a generous dousing of ignitable liquid) and often fire extinguishment procedures. Finally, it is sampled by the fire investigator and brought to the laboratory. Chapters 4 through 6 and Chapter 12 describe some of these steps, leading to a better understanding of what constitutes a fire debris sample.

1.3.2 Examination Steps

The examination of fire debris is carried out in five steps as shown in Figure 1-2.

FIGURE 1-2 The different steps of the examination of fire debris samples in order to determine the presence of ignitable liquid residues.

A/ Preliminary Examination

Before performing any types of destructive or nondestructive analysis of the sample, the criminalist proceeds to a preliminary examination of the debris (see Chapter 10). This usually consists of simply observing the content of the debris and possibly conducting an olfactory examination. The goal of this examination is threefold: First, it is to obtain any information regarding the possible presence of an ignitable liquid. This information is vital to the choice of the proper extraction technique. Second, it is to determine the nature of the debris. This is useful in the choice of the proper extraction technique and it is needed to properly interpret the final results. Finally, it is to determine whether other physical evidence of forensic interest are present and if so, to proceed with their preservation and to identify the proper sequence of examination in integration with ILR extraction.

B/ Extraction

This step, also referred to as isolation, consists of removing any (volatile or semivolatile) ignitable liquid residues that may be present in the debris so that it is in a form suitable for their subsequent analysis (see Chapter 11). Traces of ignitable liquid present in a sample are adsorbed onto the substrate, which is not in a suitable form for the instrumental analysis. Thus, it is necessary to isolate the ILR into a proper form, either in a liquid state (pure or in solution) or in a gaseous state. The different techniques available for the extraction step are based either on distillation (mostly obsolete), solvent extraction, headspace, or adsorption.

C/ Analysis

Once ILR are in a suitable form, analysis proceeds. This step is carried out using gas chromatographic (GC) techniques (see Chapter 8). Ignitable liquids usually are composed of tens or hundreds of different compounds (see Chapter 7), thus it is not possible to analyze the extract without first separating its components and then detecting them. Modern instrumental analysis allows for such a separation and GC is the most and only suitable technique to carry out this mission. The detection of the analytes normally is performed either by flame ionization detection (FID) or preferably, by mass spectrometry (MS).

D/ Interpretation of Results

Once the analytical data have been generated, it is possible to proceed with the most important, difficult, and delicate step of fire debris analysis: the interpretation of results (see Chapters 9 and 12). The interpretation of results consists of reviewing and analyzing the data to determine whether or not an ignitable liquid is present in the sample. The data usually consists of chromatograms obtained by the GC analysis, mass spectra obtained by the MS, and any other observations made during the examination of the debris. Whenever available, the circumstances around which the evidence was discovered and collected must be integrated into the interpretation. The criminalist does not stop at determining whether an ignitable liquid is present or not. He or she must characterize the liquid present in the debris, which typically is done by categorizing it, for example following the classification of ASTM International [12, 13].

E/ Report Writing and Court Presentation

Once the data have been interpreted and the conclusion reached, the criminalist prepares a report outlining the items of evidence examined, the examinations carried out, the results obtained, and the conclusions reached. This report must be succinct but comprehensive and understandable to the layperson.

Additionally, in some countries, and more particularly in the United Kingdom and the United States, the criminalist often is called to testify in court. In such instances, the expert witness must appear at trial. After qualifying as an expert, he or she must explain the examinations performed on the different items of evidence and present the results obtained as well as the conclusions reached. It is usually at this stage that any irregularities in the work performed or any misinterpretations of the results are brought to light, which may invalidate the criminalist’s work. This reminds any forensic scientist how important it is to perform any forensic examinations with the greatest care, to use solely validated scientific techniques, to follow the scientific method, and to maintain the highest standard of ethical practice.

1.3.3 Other Examinations

The main goal of fire debris analysis is to determine whether or not an ignitable liquid is present in a fire debris sample; however, there are other laboratory examination requests that are closely related to fire debris analysis. These include:

The determination of the function of an ignitable liquid.

The physical and chemical characterization (such as flash point or boiling point) of an ignitable liquid.

The determination of the source of an ignitable liquid.

The identification of an unknown liquid.

The examination of fire debris to determine the presence of chemicals susceptible of undergoing spontaneous ignition.

The determination of the propensity of a liquid to undergo self-heating and spontaneous ignition.

The examination of fire debris for the presence of other sources of ignition such as flare residues and timing device remnants.

The main reasons these examination requests are forwarded to the criminalist handling fire debris samples are either because they require the same type of instrumentation used to perform fire debris analysis or because this person is the laboratory point of contact for the fire investigator.

A/ Determination of the Function of an Ignitable Liquid

The determination of the function of an ignitable liquid (charcoal starter fluid, paint thinner, fuel, etc.) is not usually possible; however, characterization of the liquid through examination may provide some indications. Unfortunately, chemically and physically similar or even identical liquids can be used for two or more different purposes. For example, a certain liquid may be used as either a lamp oil or as a charcoal starter fluid. Additionally, a liquid intended for one particular purpose can present two different chemistries. Chapter 9 deals with this topic and presents the limitations of such a determination.

B/ Physical and Chemical Characterization of an Ignitable Liquid

In some instances, the investigation requires more information regarding a liquid than just its nature. For example, the determination of the flash point of a kerosene sample might be crucial in the evaluation of the proper functioning of a water heater (see Chapter 14). In another case, the determination of the melting point of a given fuel needs to be known to corroborate or refute a certain hypothesis. Also, the autoignition temperature of a liquid may be required information in order to evaluate a scenario involving its ignition on a hot surface. There are many examinations that can be performed on ignitable liquids and many of these fall outside the capabilities of a typical public service crime laboratory. Some crime laboratories are equipped to measure flash points, but that is about all the services available in this regard. Using private or government assay laboratories with specialized capabilities may be necessary if such examinations are requested.

C/ Determination of the Source of an Ignitable Liquid

Often, fire investigators would like to know where a given ignitable liquid comes from. It is not uncommon that a jug containing remnants of gasoline is found at a fire scene or within the vehicle of a suspect. Many times, the investigator also collects gasoline from a gas station and submits all these samples to the crime laboratory, asking whether or not the samples of gasoline have a common source. Determination of the identity of a source in fire debris analysis is a very delicate field and is usually not possible. It is often possible to exclude a common source between two samples, but the ability to infer common source between two samples is extremely limited. Detailed information regarding such examination and the subsequent interpretation of results is provided in Chapter