Failures and Improvements
in Fire Investigation
Before the mid 1990s, fire investigation relied heavily on previous cases, physical observations, and use of process of elimination. If an investigator had seen or heard about a similar fire, they would assume that the case they were investigating had the same cause. If they were unable to find an obvious source, it was common for investigators to assume the fire was started intentionally. Very little scientific work was done beyond testing materials for accelerant use. Most of the investigation was conducted on scene or through eyewitness testimonies. The use of only these methods and ignorance about sound, scientific method based investigation led to many wrongful convictions and inaccurately drawn conclusions. Nothing can be learned or gained from a superficial and inadequate investigation. False claims and the use of circumstantial evidence can destroy lives and legacies as well as diminish the benefit of knowing the true cause of a fire and preventing a similar one in the future.
Until the National Fire Protection Agency’s release of A Guide for Fire and Explosion Investigation, commonly referred to as NFPA 921, in 1992[1] it was common for investigators to follow their first instinct and conduct their investigation assuming it was true. This guide to investigating structure fires and explosions encourages the development and testing of multiple hypothesis instead of only the most apparent one.[2] In chapter four section 4.36, the NFPA 921 states that “The investigator does not have a valid or reliable conclusion unless the hypothesis can stand the test of careful and serious challenge.” [3] Taking such measures and ruling out any accidental cause is imperative before accusing someone of arson and convicting an innocent person. The advancements in fire investigation can be seen clearly when examining false arson convictions, what led investigators to these conclusions, and the improvements that have pushed the field forward and allowed those falsely convicted to be proven innocent.
Prior to the release of NFPA 921, it was not uncommon for false convictions of arson to occur. The Innocence Project, a national organization which works to exonerate those who have been falsely convicted, states “Before 1992, there was no standardized guide for investigating fires, and fire investigators didn’t have specific education requirements.”[4] The lack of unity throughout the field of fire investigation caused inconsistencies and discouraged the use of one standardized, thorough process that would help avoid mistakes or inaccuracies. NFPA 921 is now the standard for public and private investigators as well as being commonly referred to in court . Many of these false convictions were later overturned in light of new evidence or technological and investigative advancements.
One example of outdated investigative practices resulting in a wrongful conviction is the case of Cameron Todd Willingham. In 1992, Willingham was convicted and later executed for setting the fire that led to the deaths of his three daughters. The fire occurred on December 23rd, 1991, and destroyed the family’s Texas home while they slept.[5] In a 2013 article, “Junk Science and the Execution of an Innocent Man” for the New York University Journal of Law & Liberty, Paul C. Giannelli a respected lawyer and renowned expert on forensic evidence, credits the conviction to the investigator’s use of “intuition and a number of rules of thumb.” These rules of thumb were common methods and principles practiced by and passed on to American fire investigators. They demonstrate the lack of consideration that was present at the time.
Manuel Vasquez, the lead investigator of this fire, relied on his experience with arsonists instead of viewing the case with fresh eyes. For example, burns along the lower part of the walls, what appeared to be pour marks on the floor, and the fine cracks on the windows were considered to be telltale signs of arson.[6] Vasquez concluded that Willingham had used an accelerant to start the fire in his family home.[7] This claim was backed up by one of the few pieces of forensic evidence in this case. The area around the front door tested positive for accelerant. However, the investigation failed to mention that there was a grill and lighter fluid on the porch, just outside the front door.[8] The accelerant found on this sample could have easily been tracked in by anyone who walked through the door and in no way should have served as damning evidence. Vazques drew conclusions based on his past experience and relied on “rules of thumb” about what investigators at the time believed a typical arson scene should look like instead of looking further into other possibilities.
The NFPA 92, section 17.7.6.3.2 states that “Expectation bias occurs when an investigator reaches a premature conclusion without sufficient data, using the premature determination to dictate investigative processes.” Vasques quickly deduced that Willingham was guilty and therefore every piece of evidence confirmed what he already believed. Investigators are now encouraged to consider each case with an open mind instead of over relying on what they believe to be true about fires and arsonists. Vasques had already made up his mind that this fire was intentionally set and viewed every characteristic of the scene in a way that confirmed what he had already accepted to be true.
Willingham’s behavior during and after the fire also led Vasquez to suspect him of arson. Vaquez claimed that he seemed cold, distant, and unremorseful for the supposed crime during his interrogations. However, as journalist for the New Yorker David Grann wrote in his 2009 book Trial by Fire about Willingham’s case, firefighters who were on the scene claimed that Willingham had to be restrained as to prevent him from running into the burning house for his children. Willingham’s demeanor after the fire is to be expected of someone who had just endured such trauma. According to the National Center for PTSD, it is common for people to become numb or detached after experiencing a traumatic event. [9] Vasquez used his own opinions and biases to confirm what he already suspected, instead of conducting a more objective investigation.
This “demeanor evidence” is commonly used in investigations to deduce the honesty and sincerity of a person’s statement. However, in this case Vasquez failed to consider the psychological effects of being in a fire and losing one’s family in the process and used Willingham’s response against him. Demeanor evidence is often criticized as being insufficient and unreliable. A 2025 article from the Minnesota Law Review claims that the use of demeanor evidence encourages jurors to judge the accused based on their appearance rather than the facts of the case.
The circumstantial and weak evidence against Willingham was re-examined by renowned fire scientist Dr. Gerald Hurst in early 2004. Dr. Hurst reported that the investigation was based on outdated “junk science.”[10] In his report to the Navarro County District Court, he referred to many of what investigators at the time considered to be signs of arson as “old wives’ tales.” For example, the brown stains on the floor that appeared to be pour marks are often the result of a flashover event.[11] Even at the time of the investigation the methods Vazques used were considered insufficient by experts. Dr. Hurst signed off on his report on February 13th, 2004, just four days before Willingham’s execution. Unfortunately, Willingham was unable to be saved, and his execution represents failures in fire analysis and the legal system.
Years after his execution, Willingham’s innocence was finally proven. In 2011, Fire scientist Craig Beyler determined that the lack of uniform methods in fire investigation at the time led to a wrongful conviction.[12] Beyler claimed that Vasques did not properly examine nor interpret the evidence present and there for could not come up with a guaranteed cause of the fire. The evidence used in his conviction should not have been sufficient to draw any sort of firm conclusion. New standards such as those outlined in NFPA 921 as well as new forensic technologies work to ensure that a situation like this does not happen again. NFPA 921 was published in the same year as Willingham’s conviction and debunked the investigative practices damned him. Unfortunately, this guide was not widely accepted or implemented by investigators until years later. This case demonstrates why thorough and dedicated investigation is so important. It exemplifies why it is necessary for investigators to inspect every possibility instead of working to confirm what they already believe to be true.
Another example of a wrongful arson conviction is Ernest Ray Willis who was sentenced to death in 1986 and remained on death row for seventeen years before his exoneration in 2004.[13] Willis was charged with the murder of two women when the home he had been staying in while out of work caught fire. Like Willingham, the evidence used against him lacked substance and forensic proof. Both convictions were greatly based on the behavior and demeanor of the accused during their trials and questioning. The same passed down notions about fire investigation that led to Willingham’s conviction were used against Willis.
Unsubstantial forensic evidence played a role in Willis’s conviction. Fire investigators saw what appeared to be pour marks on the floor and drew conclusions without confirming that they actually were.[14] There was no other forensic evidence that suggested the fire had been intentionally set and Willis had no reason or motive to commit such a crime. One weak piece of evidence coupled with the lack of injuries Willis sustained led investigators to suspect him of arson.
His “vacant stare”[15] and lack of expression led jurors and investigators to believe that he was guilty. His impassivity can be largely attributed to the high dose of antipsychotics he had been given.[16] Willis was prescribed these medications to help alleviate his chronic back pain that stopped him from working, but when evaluated, did not display symptoms of psychosis. This information should have been made available and taken into consideration when making any sort of conclusion about his reaction to the fire or court room proceedings. Willis’s attorney failed to defend him or provide proper legal counsel during the trial, neglecting to make sure crucial facts were known by the jurors and judges.[17]
Eventually, Willis’s case was reevaluated, and he was proven innocent of the crime. New investigators found no evidence that the fire was not accidental. They discovered that the house had electrical issues which could have started the fire.[18] This possibility had not been originally considered. The appeals court determined that the effect of the antipsychotics was unfairly used against Willis during his original trial and that he was not dangerous.[19] Willis was released after seventeen years on death row for a crime he never committed. He was able to live the rest of his life as a free man but could never recover the years he spent in prison.
In the cases of Willingham, and Willis, outdated practices and quicky drawn conclusions lead to their wrongful convictions. The pseudoscientific and unsubstantial evidence used against these men should not have been sufficient to sentence them to death, but at the time it was. Reconsideration of the evidence used in these investigations through the lens of new technologies and standards led to both being proven innocent, even if it was too late for them to enjoy their innocence. With new investigative requirements and legislation, investigators and law enforcement must examine every possibility instead of the one they think is the most likely.
Section 18.6.2 encourages the use of fire modeling to test a hypothesis on fire origin. Fire modeling can recreate the scene and how a fire would behave if it started in different locations or conditions. This technology would have proved useful in both previously mentioned cases. It would have allowed investigators to test their theories on the fires’ origins. The access to advanced technology such as fire modeling gives modern fire investigators a way to consider many possibilities that former fire investigators did not have.
Because previous fire investigators lacked systematically set methods and requirements when performing an investigation, they relied on what they knew. While fire investigation has always required some form of training and strong critical thinking skills, there is now a set process that must be taken for one to become a certified investigator. Potential investigators must first spend time working for a fire department, then complete the training and education required for their potential employer. This can include a bachelor’s degree in science or a training school through a federal organization. Once they have completed their must enter a probationary period at their place of employment before becoming fully certified fire and explosion investigators.[20]
Modern investigators know that pour patterns, and low burning are characteristics of an extremely hot fire but are not directly caused by using an accelerant. Crazed glass can be caused by water from a fire hose rapidly cooling the glass and not accelerant use. Investigators are now able to virtually reconstruct scenes after a fire takes place to observe every possible way a fire could start or spread. Matthiesen, Wickert & Leher, S.C. Americans Subrogation Law Firm suggests that any insurance appraiser should make sure that a fire investigator is well versed in the methods and requirements laid out in NFPA 921.[21] NFPA 921 marks a huge step forward in fire investigation. It provides specific outlines and limits an investigator’s ability to rely on anecdotal experience or generalizations.
NFPA 921 covers things from how a camera can be used on scene, to determining the cause of death in fire victims. The guide is updated about every three years in response to advances in law or technology. The most recent version came out in 2024 and can be accessed online or purchased as a book. Because this guide goes into such extensive depth about how to investigate many different types of fires, it ensures that investigators come to the most reliable and accurate conclusion possible.
While modern fire investigation is not a perfect science and still shows room for improvement, it has become vastly more reliable in recent decades. The unfortunate false convictions of Willingham and Willis forced courts, legislators, and investigators to reconsider the things they believed to be true. By sticking to the regulations outlined in NFPA 92, investigators can ensure the accuracy of their conclusions, preventing false accusations and ensuring future safety.
Bibliography
Balleza Maureen. “Death Row Inmate No More, Texan Walks Free to a New Life.” New York Times, October 8, 2004. https://www.nytimes.com/2004/10/08/us/death-row-inmate-no-more-texan-walks-free-to-a-new-life.html
Brennan-Marquez Kiel and Kerr-Simon Julia, “Judging Demeanor.” Minnesota Law Review, April 30, 2025. https://minnesotalawreview.org/article/judging-demeanor/
“Contributing Factor Fire Investigation” 2024, The Innocence Center, March 18, 2024. https://theinnocencecenter.org/resource/fire-investigation/
Dr. Gerald Hurst, Report of Dr. Gerald Hurst, Navarro County Texas, 2004. https://www.scribd.com/document/337/Gerald-Hurst-s-Report-on-Todd-Willinghsm-Arson-Investigation
Grann David, “Trial by Fire, Did Texas Execute an Innocent Man,” The New Yorker, August 31, 2009. https://opencasebook.org/casebooks/5959-advanced-evidence-spring-2025/resources/3.7.1-trial-by-fire-did-texas-execute-an-innocent-man/
Gross Alexandria. “Ernest Ray Willis.” The National Registry of Exonerations, August 29, 2011. https://exonerationregistry.org/cases/10972
Katherine A. Sandoval. “NFPA 921 Standards Have Changes: What Claims Adjusters Should Know.” 2021, Matthiesen, Wickert & Lehrer S.C. September 27, 2021. https://www.mwl-law.com/nfpa-standards-have-changed-what-every-claims-adjuster-should-know/
National Fire Protection Association, NFPA 921, Guide for Fire and Explosion Investigations, 2024 ed. National Fire Protection Association, 2023. https://link.nfpa.org/free-access/publications/921/2024
Paul C. Giannelli. “Junk Science and the Execution of an Innocent Man,” New York University Journal of Law & Liberty 7, no. 2 (2013) https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1917454
“Report Documents the Execution of an Innocent Man in Texas” eji, August 2, 2009. https://eji.org/news/report-shows-texas-executed-innocent-man-cameron-todd-willingham/
Santos, Fernanda. “Advances in Science of Fire Free a Convict After 42 Years.” New York Times, Apr 03, 2013. https://umw.idm.oclc.org/login?url=https://www.proquest.com/newspapers/advances-science-fire-free-convict-after-42-years/docview/1814901276/se-2.
Smith Jordan, “Innocent Man Off Death Row,” Austin Chronicle, Texas October 15, 2004. https://www.austinchronicle.com/news/innocent-man-off-death-row-11720258/
Smith Jordan, “Long-Awaited Testimony Rejects Arson Conclusion,” Austin Chronicle, Texas January 14, 2011. https://www.austinchronicle.com/news/long-awaited-testimony-rejects-arson-conclusion-11750200/
Staff, NPR, “Arson Forensics Sets Old Fire Myths Ablaze,” NPR, November 19, 2011. https://www.npr.org/2011/11/19/142546979/arson-forensics-sets-old-fire-myths-ablaze
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[1] National Fire Protection Association, NFPA 921, Guide for Fire and Explosion Investigations, 2024 ed. National Fire Protection Association, 2023.https://link.nfpa.org/free-access/publications/921/2024
[2] Katherine A. Sandoval. “NFPA 921 Standards Have Changes: What Claims Adjusters Should Know.” 2021, Matthiesen, Wickert & Lehrer S.C. September 27, 2021. https://www.mwl-law.com/nfpa-standards-have-changed-what-every-claims-adjuster-should-know/
[3] National Fire Protection Association, NFPA 921, Guide for Fire and Explosion Investigations, 2024 ed., 26, National Fire Protection Association, 2023.https://link.nfpa.org/free-access/publications/921/2024
[4] “Contributing Factor Fire Investigation” 2024, The Innocence Center, March 18, 2024. https://theinnocencecenter.org/resource/fire-investigation/
[5] Paul C. Giannelli. “Junk Science and the Execution of an Innocent Man,” New York University Journal of Law & Liberty 7, no. 2, 221 (2013) https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1917454
[6] Gianelli, 227-228.
[7] Dr. Gerald Hurst, Report of Dr. Gerald Hurst, Navarro County Texas, 2004. https://www.scribd.com/document/337/Gerald-Hurst-s-Report-on-Todd-Willinghsm-Arson-Investigation
[8] Gianelli, 229
[9] U.S. Department of Veterans Affairs. 2024. “Common Reactions after Trauma – PTSD: National Center for PTSD.” Www.ptsd.va.gov. March 19, 2024. https://www.ptsd.va.gov/understand/isitptsd/common_reactions.asp.
[10] “Report Documents the Execution of an Innocent Man in Texas” eji, August 2, 2009. https://eji.org/news/report-shows-texas-executed-innocent-man-cameron-todd-willingham/
[11] Dr. Gerald Hurst, Report of Dr. Gerald Hurst, Navarro County Texas
[12] Smith Jordan, “Long-Awaited Testimony Rejects Arson Conclusion,” Austin Chronicle, Texas January 14, 2011. https://www.austinchronicle.com/news/long-awaited-testimony-rejects-arson-conclusion-11750200/
[13] Balleza Maureen. “Death Row Inmate No More, Texan Walks Free to a New Life.” New York Times, October 8, 2004. https://www.nytimes.com/2004/10/08/us/death-row-inmate-no-more-texan-walks-free-to-a-new-life.html
[14] Gross Alexandria. “Ernest Ray Willis.” The National Registry of Exonerations, August 29, 2011. https://exonerationregistry.org/cases/10972
[15] Smith Jordan, “Innocent Man Off Death Row,” Austin Chronicle, Texas October 15, 2004. https://www.austinchronicle.com/news/innocent-man-off-death-row-11720258/
[16] Belleza, “Death Row Inmate No More, Texan Walks Free to a New Life.”
[17] Belleza, “Death Row Inmate No More, Texan Walks Free to a New Life.”
[18] Gross, “Earnest Ray Willis”
[19] Smith, “Innocent Man Off Death Row”
[20] Staff, Fire Science Online, “How to Become a Fire Investigator,” Fire Science Online, October 4, 2019.https://www.firescience.org/how-to-become-a-fire-investigator/
[21] Katherine A. Sandoval. “NFPA 921 Standards Have Changes: What Claims Adjusters Should Know.”