Fire Investigation Basics

Jarred R. Alden and Brian Dusseau review some of the fundamentals of fire investigations.

Investigating a fire or an explosion can be extremely time-consuming, arduous, complex, and challenging. Fire investigators (FIs) are called to scenes ranging from basic food on the stove fires to multiple fatalities and possibly murders. FIs must be meticulous, performing the same assessments and following the same systematic approach every time they are dispatched to a scene. Specificity in assessment, procedure, evidence collection, interviewing, and follow-up are all crucial when documenting. The documentation aspect must be thorough and built with factual information grounded in evidence. If an event cannot be proven through evidence, then the conclusion cannot be definitive. Because of the FI’s limitations in time, resources, and personnel, it is important for all firefighters to remain patient at the fire scene while the FIs perform their duties. It is incumbent on the fire companies to avoid excessive overhaul to reduce adversarial relationships with FIs. The obliteration of fire patterns is not only detrimental to the investigation but also a disservice to the communities we are trying to protect.

In the past, FIs have been referred to as arson investigators in some areas. However, this is changing because of the duties performed. FIs investigate more than just arson cases. They inspect every fire and explosion in the district for information on how to prevent future catastrophes, implement fire code changes, catch criminals, and identify consumer products that may need recalls.

Postfire or explosion, the officers and the FI generate and complete a fire report; the information paints a picture regarding the facts of the case: Were smoke alarms present? If so, did they operate during the fire? Did the alarm alert the occupants? If not, why not? Was the smoke alarm out of date or broken? Were there batteries in the smoke detector? This is one example of data collection that provides critical information to the fire prevention bureaus. It can be used to pinpoint specific areas of the city that may need more smoke detectors, for example.


Fire Investigation Puzzlers: Rock Salt and BX Cable

The Geometry of Fire Investigation: Interpreting Fire Patterns

Training Minutes Throwback: Arson and Fire Investigation


To truly understand the complexities of fire investigation, it is important to start with the basics.

Arson definitions vary widely, owing primarily to differing statutory terminology. The FBI’s Uniform Crime Reporting program defines arson as “any willful or malicious burning or attempting to burn, with or without intent to defraud, a dwelling house, public building, motor vehicle or aircraft, or personal property of another.”1 In addition, National Fire Protection Association (NFPA) 921, Guide for Fire and Explosion Investigations,2 defines arson as “the crime of maliciously and intentionally, or recklessly, starting a fire or causing an explosion.”

Fire is a rapid oxidation process, which is a chemical chain reaction producing various intensities of heat, light, and sound. For fire to initiate, there must be three components that combine in the appropriate mixtures: a fuel, oxygen/oxidizer, and a stimulus. A stimulus can come in the form of heat, friction, impact, shock, or electrostatic discharge. If the oxygen/oxidizer and fuel mix proportionately, then the stimulus is all that is needed for fire to form.

Explosion is a violent expansion of energy that produces shock waves, pressure differentiations, thermal effects, seismic effects, and materials propulsion into the atmosphere and environment. The intensities can vary depending on the types of explosive materials, amount of explosive materials, temperature, humidity, environment, structures, and many other factors.

Pyrolysis is the decomposition of fuels/materials. A fuel has to pyrolyze; fuels decompose producing vapors, which ignite. The fuel rises to its ignition temperature, leading to fuel decomposition, pyrolysis, and ignition.

Scientific method is a systematic procedure used to investigate a phenomenon. It is a seven-step process involving recognition, identification, collection, analysis, formulation, testing, and concluding. If the process is strictly followed and biases are excluded, determinations can be made.

NFPA 1033, Standard for Professional Qualifications for Fire Investigator,3 is a document written by a committee of legal partners, FIs, and editors used to provide a standard for fire investigations that SHALL always be adhered to. The FI’s job performance requirements (JPRs) are contained in this document. Educational requirements are contained and presented as the 16 requisite knowledge requirements. This is important for initial training and subsequent, continuing education (CE). A few of the CE requirements include, but are not limited to, the following: fire science, thermodynamics, thermometry, evidence collection, and electricity.

NFPA 921 is a document written by FIs, scientists, engineers, legal partners, and editors used as a guide in fire investigations. This document is not required when investigating a fire or an explosion; however, it is highly recommended and will more than likely be used as a reference by a prosecutor and the defense in a court of law. This guide provides information related to the numerous and various encounters while investigating. Some sections of the document include, but are not limited to, the following: fire pattern analysis, evidence collection techniques, marine fires, and electrical fires.

Evidence involves the tangible and nontangible artifacts procured at the scene and during interviews and interrogations. Evidence is rooted in FACT, not opinion. Facts tell a story that can be traced back to the origin and cause of a fire/explosion. Without evidence, a case cannot have a concrete determination. It provides the proof needed to document or articulate unbiased findings.

Determination is a finding made by an FI based on logical progressions uncovered throughout an investigation. Determinations are not made lightly and must be backed by science and evidence. There are four determination categories: Accidental, Natural, Incendiary, and Undetermined. Electrical fires would be considered accidental, while lightning strikes would fall into the natural category. Incendiary fires are intentional. Undetermined means that an FI has come to two or more hypotheses and cannot rule out one or more hypotheses because of lack of evidentiary findings.

Origin is where the fire started. There may be more than one origin. FIs read fire patterns to narrow down the origin. At times, the origin cannot be narrowed down to one specific area. A room may have to suffice as the “area of origin” if there is a lack of evidence because of severe fire damage. Multiple points of origin may lead an FI to make a determination of incendiary. The origin of the fire may also be derived from witness information and electronic data, fire dynamics, fire patterns, and arc mapping.

Cause is how the competent ignition source and material first ignited joined together, leading to a fire/explosion. We are also attempting to find what fuel was used as well as what heat source. Were there resistance issues in the wiring? Were ignitable liquids poured? Was a portable ignition source used? Understanding the cause may lead to a perpetrator if the fire was deemed incendiary.

Interview is an information-gathering session requested by the FI, prosecutor, defending attorney, witness, victim, or suspect. Interviews are conducted simply to gather the facts of the case. The questions asked are not accusatory in nature. The interview may, however, transition into an interrogation. FIs must be careful not to become accusatory without reading Miranda first.

Interrogation is a custodial meeting with a suspect who is believed to have some connection with the crime in question. Interrogations are still used to gather information like interviews; however, they may become accusatory in nature as the interaction progresses. The FI uses various psychological questioning techniques to procure a confession.

Evidence recovery from an explosion during a training exercise. The power source and the detonation device were found in the debris.

(1) Evidence recovery from an explosion during a training exercise. The power source and the detonation device were found in the debris. (Photos courtesy of authors.)

The Scientific Method

The scientific method is a structured, systematic approach used to investigate in every discipline. It is a model for analysis, trial and error, and decision making. It is dynamic and adjustable, depending on the circumstances. It has seven steps, and each is important; misunderstanding in any step can lead to a faulty conclusion and the arrests and convictions of innocent people.

Step 1: Recognize the need. The need may be to prevent subsequent fires or to arrest the guilty if the fire was intentionally set. The information from one fire, if gathered and analyzed correctly, can be used to investigate or even prevent future fires.

Step 2: Identify the problem. A fire or an explosion had occurred, and an investigation is necessary; there is also a high probability that an injury or a death has occurred. Investigating fire and explosion scenes may also reveal other dangers not initially identified such as imminent collapse of structures, hidden bodies, or electricity dangers. Fires need to be investigated to assist in the fire prevention cycle. Moreover, the fewer fires, the fewer chances of firefighter injury or exposure to toxic by-products on the firegrounds.

Step 3: Collect the data. The purpose is to determine the origin and cause of a fire, which may lead to a perpetrator if the fire is incendiary. Ultimately, fire prevention is the goal.

Common sense reigns supreme in some cases. Let’s say a house is vacant and fire companies respond to this location for a fully involved house fire. On arrival as the FI, you are told that the electric meter connection had no meter and was locked. The gas turn-off valve was locked in the “Off” position. Per the homeowner, no construction or refurbishing was ongoing in the house. This was confirmed by your own observations as you performed your investigations. A check of the weather, based on the weather service reports, showed no lightning in the area. This was corroborated by your investigation. The first-in fire officer stated that the side door was breached prior to their arrival. No ignition sources were found at the scene. There were multiple points of origin where pieces of burnt newspaper were found. What was the cause of the fire? Deductive reasoning points to a determination of incendiary caused by a person or persons using a portable ignition source such as a lighter. No other heat sources can be confirmed in the areas of origin. What’s the cause of this fire? Sometimes the absence of evidence is evidence based on deductive reasoning. This must be articulated well in the documentation of the fire scene.

Data does not have to come in the form of tangible artifacts. At times, noting what is not at the scene is just as important as what is present. Are family pictures missing? Does the merchant lack an inventory? Is there missing equipment at a manufacturer? Data collection literacy is crucial because gathering information that is not important to the case can be time consuming and may lead FIs down the wrong path. Data collection can come in the form of witness statements, victim statements, suspect statements, physical evidence, observations of fire crews, and the FI’s observations. Learning what to collect and what to disregard is difficult for the novice. Education and experiences will assist the FI with data collection relevance. The collection method is also relevant to avoid spoliation (tainting the evidence, rendering it unusable).

Step 4: Analyze the data. This can be difficult if the FI does not know how to perform this crucial function. Looking for certain cues and patterns in the data collected can lead to the formulation of a solid hypothesis. Does the collected evidence belong at the scene? Can the evidence’s relevance to the case be articulated? Does the evidence logically connect to other pieces of evidence? Does the evidence connect to a person or persons? Is the same evidence collected at all points of origin? Is the same evidence found at different house fires? Can the absence or presence of evidence lead to a change in a previous determination? Is the evidence exculpatory? Does the evidence disprove my hypothesis? Answering these types of questions is part of the analytical process. This is the meat and potatoes of being a detective.

Keeping bias out of the equation is key while analyzing data. The predetermination of a cause will likely have the FI searching for data and clues that fit a hypothesis—avoid this pitfall at all costs. Confirmation bias can cause massive destruction on many fronts. This phenomenon can convict the innocent, free the guilty, and discredit the status of the FI. There is nothing more detrimental to FIs’ careers than having their expert testimony thrown out of court for inaccuracies because of bias. Once FIs are disproven as expert witnesses, their credibility can be harmed for future cases and could ultimately end their careers.

I (Alden) was involved in an investigation where my determination was the final factor in the possible eviction of a tenant. I was dispatched to a house fire. On arrival, I found that a small fire was inside a wall next to the toilet on the second floor. The fire’s origin was inside the wall between two studs. There was a small hole in the lathe and plaster at the fire’s origin. Blown-in insulation was present at the point of origin also. The fire had dropped down and spread into the ceiling of the kitchen below the restroom. Fire companies had pulled the ceiling in the kitchen and extinguished the fire. They had also opened the wall in the restroom. I was able to observe more fire damage to the wall studs and the insulation. I had recalled from my prior training that blown-in insulation smolders for hours with little heat initiation. Once the smoldering embers find a larger combustible such as wood, the fire will grow and spread.

The fire spread up and down the studs but was stopped by the fire crews. Numerous cigarettes and a lighter were noted resting on the windowsill and around the sink in the restroom. I had asked the tenant if she smoked in the restroom. She stated that she did smoke in the restroom at times but not today. I asked the tenant where she ashed and discarded her cigarettes. She stated that she extinguished the cigarettes on the sink’s marble after wetting each one with water. I asked her if she ashed or discarded any cigarettes into the hole in the wall at the point of origin. She replied, “No.” I did not find a cigarette in the blown-in insulation. However, that did not rule out an ash or a spark. There was also no electrical heat source in the area.

This is an hourglass-shaped fire pattern used to ascertain the point of origin in a house fire.

(2) This is an hourglass-shaped fire pattern used to ascertain the point of origin in a house fire.

A few minutes after interviewing the tenant, I noticed a man walking into the rental. I approached him, identified myself, and inquired what his connection was to this fire. He stated that he was the maintenance person for the rental property. He stated that he knew the tenant smoked in the bathroom since he had been in the apartment earlier in the day. He had surmised that her smoking was the cause. I asked him why he was in her restroom. He stated that he had just installed a hot water tank in the basement. He had also snaked the soil stack in the wall from the bathroom. I had him take me to the area where he performed the work. He took me directly to the point of origin. Once I opened the wall wider, I noticed that he had used a grinding saw to cut a 4 × 4 square in the steel soil stack. He had covered it with duct tape. The tape had been burned through and resided directly above the point of origin.

After more questioning, he also stated that the grinding saw produced a lot of sparks. He had not covered the wall opening while using the saw. The friction from the saw had produced enough sparking, which had fallen into the blown-in insulation. The insulation smoldered for hours until the heated embers reached the wall studs. The studs ignited, leading to the house fire. This is a good example of letting the evidence speak the facts and the need to keep collecting data. Things are not always what they appear. Some evidence may not be evidence at all. Remember, the lack of evidence may also be a clue. The totality of the circumstances in this case had to be viewed with a wide lens. If I had had tunnel vision or let my bias control the investigation, then the tenant may have lost her rental and been on the streets.

Step 5: Formulate the hypothesis. This can be difficult and complex. Often, evidence is destroyed and indiscernible. At times, there should be evidentiary remains; however, the heat and flames from the fire/explosion may render it uncollectable. There may be no witnesses or security cameras present at the scene. Formulating a hypothesis is an inductive process. In other words, the FI is theory building, outlining a story regarding what happened prior to, during, and after the fire. Inductive reasoning requires a good educational base accompanied by great training and relevant experiences in the field. Various hypotheses are formulated; some are discarded for reasons that the FI should articulate in the report and in court. Observations, witness statements, experiments, and physical evidence are used to rule out hypotheses.

Step 6: Test the hypothesis. This is the deductive stage. Instead of building hypotheses, you use training, references, guides, standards, research, experiences, and conducting experiments to scrutinize said hypothesis. If a hypothesis cannot stand up to critical analysis in the form of a test or evidence, then the hypothesis must be discarded. One important caveat to avoid in this stage is confirmation bias—in other words, do not attempt to prove a hypothesis. Only attempt to disprove your inductive creations. If the hypothesis can stand up to every test applied, then this hypothesis is probable. We recommend peer review of a hypothesis. Alternate hypotheses must be considered and documented in the FI’s findings. The FI may have not considered all testing measures. Testing measures are not standardized to fit every fire/explosion. Thus, the more testing measures implemented, the higher the probability that the tested hypothesis is the correct one.

Step 7: Conclude. Choosing the correct hypothesis should not be complex if the first six steps were implemented appropriately. If the FI cannot choose between two or more hypotheses, then either an error had occurred in the previous steps or not enough evidence was available to confidently conclude. It is not unusual to revisit any stage in the scientific method process. Was all pertinent data collected? Was the analysis of the data accurate; was a pattern missed? Was there another hypothesis not considered? Was testing of the hypothesis accurate and was the scope wide enough to consider all possibilities? What resources were used as backup evidence? What experiments were used or researched?

A small “inverted cone” fire pattern above the point of origin. The white discoloration is a residual effect indicating that the fire’s temperature was the highest in this area. Inverted U-shaped fire patterns are usually from natural gas leaks, drop down from fires above, and incipient fires that are extinguished before growing. In this case, the fire pattern was from a small fire extinguished in its early stages.

(3) A small “inverted cone” fire pattern above the point of origin. The white discoloration is a residual effect indicating that the fire’s temperature was the highest in this area. Inverted U-shaped fire patterns are usually from natural gas leaks, drop down from fires above, and incipient fires that are extinguished before growing. In this case, the fire pattern was from a small fire extinguished in its early stages.

Be sure that a peer review is performed prior to any court proceedings. Be ready to present the findings in a manner that a novice can understand. In essence, courtroom testimony affords the FI an opportunity to teach a jury about fire behavior. Fancy investigator terms will only cause confusion and may open the door for a defending attorney to pick apart the FI’s case. Present facts in a lucid, succinct manner. The conclusion will include the final determination.

One additional note: The process of determining the origin and cause should never be conducted through a process of elimination, whereby all causes are ruled out except for one. This is called negative corpus and is not permissible. All cause determinations must be based on actual evidence and conclusions, supporting the hypothesis that has been developed.


Determinations are made based on fact. Conjecture and opinions cannot be proved. If more than one hypothesis is tested and one is not left standing, then the determination has to be ruled “Undetermined.” There are four types of determinations:

Accidental. This determination could have many causes. The premise here is that the causes are not natural or intentional. The following examples of fire cause determinations are common but not all-inclusive: unattended candles, food left unattended on the stove or in the oven, a young child playing with matches/lighter, and electrical arcing.

Natural. This determination is unusual; however, natural causes do occur. Intent is not part of the equation. Lightning strikes, floods that rip down power line structures, earthquakes that cause structural compromise, and tornadoes can all cause fires depending on the circumstances. The electrical grid could become compromised or gas leaks could occur, leading to explosions and fires.

Incendiary. Intent is the key term when referencing this determination. A fire resulting from a young child playing with a lighter and igniting the couch is not considered incendiary. The child’s age at the time of the fire is important. A five-year-old will not be held accountable for an intentional act since the mental faculties of the child are not fully developed to understand the dangers of fire. Intent shows that the person is culpable for his actions. Examples include arson for hire, setting a home on fire for insurance purposes, and setting a structure or vehicle on fire to conceal another crime. If the person is of comprehensible age and has the mental faculties to know the difference between right and wrong, then he could be held responsible for arson or aggravated arson if he sets a fire.

Motive is a consideration regarding this determination. NFPA 921 (2017 ed., pt. delineates the distinction between motive and intent. It states that intent refers to the state of mind, steps, and acts or failure to act at the time of the offense.2 The JPR listed in NFPA 1033 (2014, pt. 4.6.4) emphasizes the importance of determining motive. It states that the fire investigator shall “establish evidence as to motive and/or opportunity, given an incendiary fire, so that the evidence is supported by documentation and meets the evidentiary requirements of the jurisdiction.” In describing intent, an investigation should show “purposefulness or deliberateness of the person’s actions or omissions.”

Motive is defined as the “inner drive or impulse that is the cause, reason, or incentive that induces or prompts a specific behavior.”1 In the case of criminal investigations and prosecutions, proof of motive, unlike intent, is not required. However, in criminal cases, presenting a plausible motive for a defendant’s arson makes it easier for the trier of fact (judge) to find that a fire was incendiary and to connect the defendant to the fire. See cited cases State v. O’Haver, 33 S. W.3d 555 (Miss. Ct. App. 2001) and Briggs v. Makowski, 2000 U.S. Dist. LEXIS 13029 (E.D. Mich. 2000).1

Motive establishment should not be the glue that holds the cause determination together and should be approached with caution. NFPA 921 clearly states in pt., “Motive indicators should not be included or substituted as analytical elements of the fire scene for the purpose of determining or classifying the fire cause. The proper use of motive indicators in the fire investigation process is in identifying potential suspects only after the fire origin and cause have been determined and the fire has been classified as incendiary.”2

Undetermined. Concluding that a fire is undetermined serves a purpose. Again, if a single hypothesis does not stand alone, then a conclusion cannot be definitive. When an FI tentatively concludes that a fire/explosion is undetermined, this allows time to develop the case further. The FI may search for more evidence (gather more data), contact more witnesses, ask more questions, retest hypotheses, test new hypotheses, or locate a suspect—leaving the investigative door open for more information to augment and strengthen the case. Regardless of the cause reached, FIs should keep in mind that they are ultimately truth seekers.

A large U-shaped fire pattern. The lines of demarcation angle down to the point of origin and show the heavy soot in the black, charred area of the block. The clean area underneath shows that the soot from the fire did not bank down to the floor. The fire was extinguished before the smoke made it all the way to the floor. The origin in this fire was on the bed, which is evidenced by the heavy mass loss.

(4) A large U-shaped fire pattern. The lines of demarcation angle down to the point of origin and show the heavy soot in the black, charred area of the block. The clean area underneath shows that the soot from the fire did not bank down to the floor. The fire was extinguished before the smoke made it all the way to the floor. The origin in this fire was on the bed, which is evidenced by the heavy mass loss.

Evidence and Expert Testimony

Maintaining the status of expert witness in a court of law comes with many roles. There is also a juxtaposition that comes with this status in the form of serious accountability. Being an expert witness is not taken lightly. Having the proof in the form of evidence can make or break a case and an expert witness’s credibility.

Cases cannot be proved by FIs who have no proof. Credible evidence provides all parties involved with factual data that is difficult to dispute as long as policies and procedures are followed. An FI’s status grows symbiotic as the case evolves. FIs are actually part of the evidence presented in court because they can use observations and training as part of the evidentiary explanation. Interpreting fire patterns is a good example of this. Furthermore, FIs also act as conduits between the scene and the courts. They are the eyes and ears, reporting the facts of the case. Articulation of fire behavior to the jury layperson is not an easy feat. However, if done correctly, it will only bolster the case. Documentation must be exact, factual, and descriptive. Thorough documentation can help FIs convey to a jury the totality of the circumstances.

Evidence has the potential to be thrown out of court if the collection processes are not procedural and untainted. The use of gloves and proper collection methods is paramount. Photography is one form of documentation used to show that evidence was collected and processed properly. Using tools to collect evidence that have not been cleaned is one example of spoliation. Cross contamination from someone else’s DNA could taint the recently collected evidence. Improper storage of evidence can also lead to spoliation. Placing clothing in a plastic bag and sealing the bag can damage the contents if bodily fluids are present on the clothing. This type of evidence would need to be stored in paper bags to allow proper ventilation of the contents.

Expert testimony is simply the FI’s presentation of opinion regarding the fire’s origin and cause. The FI is deemed an expert because of the training and experience needed to investigate a fire or explosion. The days of FIs simply testifying their findings without evidentiary support are long past. Defendants have been wrongly accused and imprisoned because of FIs’ faulty testimony. Before much-needed legal requirements were introduced, only years of experience were used to validate an FI’s findings.

Some of the knowledge once thought to be scientific was ironically not based in science. An example of this is spalling. Spalling occurs when brick and block crack; pieces then pop off from the extreme heat. In years past, investigators maintained that spalling was solely from an ignitable liquid being poured on the brick or block. This false supposition has been proven wrong through scientific experimentation. When FIs were pressed by defending attorneys to expound on their findings, most employed, “ipse dixit.” It is an assertion without proof or an expression of opinion.

Asserting without proof is dangerous and can end careers. Case law changed the fire investigative world forever with the implementation of the ruling from Frye v. United States, in which the courts ruled that expert testimony must be based in science. The scientific methods must also be generally accepted by peers residing in the same scientific community. This is referred to as the Frye Standard or Frye Test. This also incorporates the principles, procedures, policies, and techniques used in said community of scientists. Not all states still use the Frye Standard in court though. The Daubert Standard was adopted by some states as the litmus test used by the courts.

In Daubert v. Merrell Dow Pharmaceuticals, Inc., the premise of the case also revolved around expert testimony. While the facets of the actual case are not related to fire investigations, the underpinnings and legal aspects of the case apply to any expert testimony used in a court of law. Rule 702 (Federal Rules of Evidence) states that the judge is the gatekeeper who determines if the expert witness’s testimony is rooted in scientific knowledge. Moreover, to educate the trier of fact regarding the science used in court, a witness who qualifies as an expert may testify if educated, trained, and experienced in the topic of discussion. This rule was used in the Daubert case. The proclamation of education, skill, training, and experience alone does not preclude the expert from being scrutinized, however. The Daubert case and two other cases were combined to develop the Daubert Standard regarding a witness’s testimony being considered “expert” and if the testimony was admissible. A Daubert Motion may be made to strike a witness’s testimony from court if certain prongs are not met. In other words, if the expert witness is asked to provide scientific and technical explanation and interpretation, then certain standards have to be met in the explanation and interpretation. These prongs that test an expert witness’s testimony for validity and reliability include the following: Has the method or technique been tested in actual field conditions, not just within the confines of a lab? Has the method or technique been reviewed by peers in the same scientific community, and has it stood up to scrutiny? Does the method or technique have an error rate? Are there failures, and what are the percentages? While performing the method or technique, does a standard exist that is applicable in all cases? Is the method valid and reliable? Is the method or technique an accepted practice in the same scientific discipline?

Kumho Tire Co. v. Carmichael is another case that involves expert testimony. Who is considered an expert? Does the expert have to come from the scientific community for the testimony to be admissible in court? The tire technician’s method of ruling that a tire blowout in this case was from a defect in the tire was erroneous. The technician did not find a defect; he could not find any evidence of other causes, which led him to deduce a defect in the tire. The Daubert Standard applied in this case because there was no definitive distinction between what is deemed scientific and technical expertise. All “expert” testimony must be scrutinized using the Daubert Standard. The testimony does not have to be scientific to fall under the testing prongs used in Daubert. In a nutshell, the focus is on who is an expert witness and what methods are used to make conclusions that will be used in a court of law.

Another case that had a profound impact on the fire investigative world is General Electric Co. v. Joiner. The FI is required to have adequate evidence presented to the prosecutor. The prosecutor will present these findings as part of the government’s discovery prior to trial. Discovery gives the defense the information needed to view the charges in full and to analyze the methods and rationale used to conclude the guilt of the accused. Without presenting discovery to the defense, the prosecution cannot proceed. The evidence the FI provides must not have any gaps or inconsistencies. In other words, the evidence must proceed logically to the conclusion. Without proper evidence, a determination, excluding Undetermined, would be considered arbitrary and possibly capricious. If this is the case, then the expert witnesses’ testimony may be excluded.

Witness Statements

Witness statements may come in the form of victim statements or even suspects’ statements. Statements made by anyone connected to the case are extremely important. Statements, once verified to be credible and accurate, may change the course of an investigation. Statements can either corroborate other evidence procured or may even render evidence faulty or irrelevant. When the fire scene is too damaged from fire, explosion, or overhaul, a statement may prove to be valuable and the only piece of certain evidence.

I (Alden) investigated an attached garage fire where the fire had damaged the inside of the garage to the point that the area of origin was reduced to a black char. The couch in this area had been totally consumed except for the springs. Nothing remained in the area that was discernible except for the couch springs and a few wires from a saw, which had melted into a blob of plastic and wiring. After the area had been cleared out by fire companies to analyze the fire patterns, a V-shaped fire pattern was found on the garage wall pointing down to the foundation and the concrete flooring. Much debris was found at the point of origin; however, the debris had been reduced to a char. At that point, I had no heat source except for the wiring at the point of origin. The outlet was across the room. This outlet had no damage and was the same for the electrical cord on that side.

I was finally able to make contact with the homeowner, who was sitting in his car across the street. He stated that he did not know what started the fire. His girlfriend was sitting in the front passenger’s seat. She was very quiet, which I found unusual. I asked her if she knew what caused the fire. She didn’t answer my question but provided a detailed explanation of what she saw. She stated that when she woke up in the middle of the night to get a drink of water in the kitchen, she saw smoke pushing into the house under the door leading to the garage. She opened the door and saw heavy fire in the A/D corner of the garage. She closed the door and called 911. Her observations corroborated the fire patterns on the door and in the garage.

She was asked again if she knew what caused the fire. She paused, put her head in her hands, and began to cry and apologize. She stated that she was smoking in the garage on the couch. She was ashing into a thin plastic coffee cover. She stated that she may not have put her cigarette out but left it smoking when she went in for the night. Two hours later was when she noticed the smoke. Without this witness’s statement, my determination would have had to be Undetermined since my physical evidence was destroyed by the fire. After her statement, we were able to locate the lid, which had melted into other objects in the area. The melted conglomeration was pulled apart and analyzed. Many burnt cigarette filters were found inside. Unattended smoking was the cause of the fire.

Ideally, having witness statements that match the physical evidence is one main objective. However, many reasons for a lack of connectivity remain. Unfortunately, one reason for this discordance is a lack of honesty. People will not provide information or will alter the truth. The majority of the time, people believe that they will get into trouble. Others feel embarrassed, while others don’t want to upset or disappoint their loved ones. Some folks perceive that an admission of guilt to an accidental fire is like admitting fault at a motor vehicle accident. For example, they erroneously believe that if they admit to accidentally leaving unattended food on the stove (consequently starting the fire), the insurance company will deny their insurance claim.

There are others, though, who are concealing a crime. Concealment usually manifests with insurance fraud being the underpinning. Some people owe back taxes or cannot pay for the structure or property any longer. To cut their losses, they burn it down and collect the insurance money. Arson to conceal murder is another tactic. It can be very difficult to investigate a fire involving a murder. Many government entities become involved, and the complexities grow.


Do not take documentation lightly. Our quality assurance manager states religiously to the medics, “If you didn’t document it, then it didn’t happen.” It also applies to fire reporting and investigations. As medics, we are the eyes and ears of the doctors and nurses. As FIs, we are the eyes and ears of the prosecutors and fire administration. “Painting a picture” with words for the receiving parties provides important details when solving cases and determining origin and cause. Every detail must be scribed, even if FIs cannot come to a definitive determination. These details may prove to be critical pieces of the investigation later.

Document a fire scene with care. It must be rooted in fact, not conjecture. If the facts reveal a pattern leading to a cause, then the scientific method was used correctly. Documenting the pertinent negatives will give insight into the origin and cause as well. It is similar to documenting a patient denying shortness of breath, chest pain, nausea/vomiting, and other symptoms. The more information gathered, even if not present, gives the FI a better idea of the cause. It is a deductive process. Remember to look for what should be at the scene that is not; look for what shouldn’t be there that is present; and look for what is present that, in fact, should be there based on training and experience.

Include the entire investigative process in the documentation. This is also true for any additional evidence or information that may surmount later in the case. Perform the investigative process and the documentation the same way every time. Defending attorneys will look for any inconsistencies they can find. The procedures and methods used to investigate and document other fires will be scrutinized. The focus may be on the FI’s processes from another case. These former processes, if different from the current methods used, will need to be explained. Why did the FI use a “right-handed” photography process at fire A but a “left-handed” photography process at fire B? A simple answer might be that the FI could not use the right-handed method because of the layout of the structure. Moreover, maybe the FI switched tactics because the majority of the fire damage occurred in the area where he normally begins the documentation process. It is recommended practice to document and investigate from the least amount of damage to the most amount of damage. Whatever method you use, make it consistent if possible.

Following a strict set of rules in investigations is not just a recommendation. Following protocols, policies, and procedures will pay off if the case makes it to court or a deposition. Insurance company investigators will also rely on accurate reporting for their investigations. Providing the most detailed and accurate information in a fire investigation report is beneficial for all parties involved. The only way to investigate a case is to use the scientific method as a paradigm. Adhering to NFPA 1033 and NFPA 921 provides the prosecution and the insurance companies with peace of mind, knowing that the FI used the scientific community’s standards and guidelines, respectively.


1. Icove, D.J. and Haynes, G.A. (2018) Kirk’s Fire Investigation, 8th Edition.

2. National Fire Protection Association 921, Guide for Fire & Explosion Investigations (2014), NFPA Publications, Quincy, MA: 8th Edition.

3. National Fire Protection Association 1033, Standard for Professional Qualifications for Fire Investigators (2014), NFPA Publications, Quincy, MA: 8th Edition.

Jarred R. Alden is a lieutenant, paramedic, and operations officer for the Akron (OH) Fire Department. He has 17 years of experience as a firefighter and 15 years as a paramedic. He also is a rescue/recovery SCUBA diver. Alden joined the Tactical Medic team in 2010 and is a SWAT/TEMS paramedic for the Akron Police Department’s SWAT team. He is an arson investigator and has investigated multiple blast scenes where explosives were used. He has presented explosives, blast injuries, tactical triage and treatment, and behavioral science classes throughout the country. Alden has a master of arts degree in applied behavioral sciences from Wright State University in Dayton, Ohio, and a baccalaureate degree in sociology/criminology from Urbana University in Urbana, Ohio.

Brian Dusseau is a fire investigator, a certified Level II firefighter in Ohio, and a certified paramedic. He has an associate degree in fire protection technology from the University of Akron. He is also a graduate of the National Fire Academy’s Fire Investigation: Interview and Testimony R0208 course for fire investigators. He has an Ohio Peace Officer certification through the state of Ohio. He is a certified evidence collection technician through the International Association of Arson Investigators. He has more than 20 years of experience in the fire service including eight years as a tactical medic. Dusseau has presented on explosives and fire investigations at the Ohio Tactical Officer’s Association conference with the Akron Fire Department’s Fire Investigation’s Bureau and the Federal Bureau of Investigation.

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