Arson is the fire of the mind. It is the legal fusion of a chemical reaction with human intent. And yet, scientific investigations are calling into question these forensic judgments. So it is that fire science can rebalance the scales of justice.1

In one generation, the canons of arson investigation have been rewritten by the scientific method2 and codified by the National Fire Protection Association (NFPA) in “NFPA 921: Guide for Fire and Explosion Investigations” (current ed. 2011; next ed. 2014).3

Commenting on this development, noted expert John Lentini ( has observed: “The most important result of the publication [NFPA 921] was not, however, the debunking of the mythology of arson investigation; it was the statement that fire investigation should be conducted according to the scientific method.”4

Indeed, NFPA 921 has been gaining acceptance by the courts. Unfortunately, the view that fire investigation is an art rather than a science is an ember slow to extinguish.5

The Ultimate Issue

In People v. Grutz, 212 N.Y. 72, 82 (1914), the Court of Appeals took to task a fire marshal who gave an opinion on the ultimate issue. He had testified that a house had been intentionally set ablaze. Thus, the court decided:

This is not a case for expert opinion. The physical facts, which are the subject of investigation, are so simple that they can be readily understood when properly described, and it is then for the jury to draw the appropriate conclusion.

Nearly a century later, the court revisited the ultimate issue rule from a new perspective.

Convicted of setting two apartment house fires, the defendant in People v. Rivers, 18 N.Y.3d 222, 225 n.1 (2011), claimed that testimony by prosecution witnesses had violated Grutz:

The fire marshal who investigated the first fire…testified that there are three causes of fires, “[a]ccidental, natural and non-accidental,” and that the fire was neither natural nor accidental but must have originated “[i]n the vapors of a flammable liquid that was introduced to the steps.”

But the court reasoned that adherence to Grutz, the minority view nationally, was inconsistent with recent Appellate Division decisions. They pointed out:

[A]n arson expert may testify to a reasonable degree of scientific certainty that, based on the expert’s investigations, all possible natural and accidental causes of the fire had been eliminated—thus eliminating all but intentional causes.6

Thus, the door has been opened for prosecution experts, but not enough to admit unreasonable and unfounded conclusions.

In People v. Richardson, 55 A.D.3d 934 (3d Dept. 2008), a fire in defendant’s home led to charges of arson and insurance fraud. The fire began in his kitchen where a score of appliances had been plugged into a single power strip.

At trial, the two arson investigators offered their conclusion that it could not have been accidental. And laboratory analysis of the baseboard in the kitchen area revealed a medium petroleum distillate. Nonetheless, the Appellate Division found this circumstantial evidence insufficient.

The investigators could not identify the specific cause of the fire nor did they examine any of the appliances as possible sources. Indeed, during their inspection they observed that three of the circuit breakers had been tripped, but did not inquire or trace them to specific appliances. Even the report of an engineer, eliminating electrical fire as the cause, had been based on analysis of the space heater and power strip without visiting the scene.

Thus, the prosecution evidence did not adequately remove the likelihood that the fire was electrical, hence accidental.

Furthermore, the distillate found at the scene had not been identified. This was another significant oversight since the defendant offered testimony that he had been repainting the kitchen and left a can of paint thinner near the space heater. And even the burn patterns on the kitchen floor did not test positive for distillates.

The inadequate investigation and failure to explore or exclude other reasonable scenarios, combined with an absence of motive, warranted reversal. Still, the “scientific certainty” embraced by the Court of Appeals in Rivers needs to be vetted by a cautious scientific approach.7

Not Always the Gold Standard

The recognition of NFPA 921 as the gold standard of practice continues to grow, but some courts view it as non-exclusive, going to the weight, not the admissibility, of the fire investigator’s evidence.8

For instance, in Schlesinger v. United States, 2012 U.S. Dist. LEXIS 15754, at 3-6 (E.D.N.Y. Feb. 6, 2012), the court contended with cause-and-origin evidence based on the distinction between the prosecution’s negative corpus delicti theory (absence of accident alone equals arson) and NFPA 921′s “process of elimination” (fact-based scientific method relying on observation, testing and evidence).

Judge Arthur D. Spatt concluded: “[A] failure to follow the methodology in NFPA 921 does not automatically require the exclusion of expert testimony on the cause and origin of a fire.” It only went to weight, not admissibility.9

Yet, a decade earlier in Royal Ins. of Am. v. Joseph Daniel Constr., 208 F. Supp. 2d 423, 426-28 (S.D.N.Y. 2002), the plaintiff insurance company had sued the defendant construction business over a claim paid out due to fire damage. Their expert determined that the defendant’s employees caused the fire, which resulted in more than half a million dollars in damage to the building they were working on. In this instance, the expert testimony withstood a challenge to its admissibility because it followed the methodology of NFPA 921:

A comparison of McGinley’s [plaintiff's expert] methodology and the six steps of the NFPA 921 methodology reveals that his conclusions were based on these recognized standards and not merely his subjective belief.

Thus, it met the tests of both Daubert and Federal Rule of Evidence 702.

And, most recently in Werth v. Hill-Rom, 856 F. Supp. 2d 1051, 1060 (D. Minn. 2012), the court granted defendant’s motion to preclude the causation opinion, because the plaintiff’s expert did not reliably follow NFPA 921:

Even if the experts had properly disclosed their reliance on NFPA 921, this would not automatically render their opinion admissible. Although NFPA 921 has achieved general acceptance in the fire-investigation community, an expert purporting to invoke it must show he applied the methodology reliably to the facts of the case.

Evidence Inflation

Less than compelling circumstantial evidence of arson might convince a jury when it is bolstered by an expert’s testimony. Indeed, unscientific methods often inflate the credibility of otherwise lackluster proof, i.e., the CSI effect. And, no evidence can be purified of an expert’s gloss.

Weak circumstantial proof, dubious evidence of motive, and confirmation bias can all be shored up by unreliable, unscientific methods.10 This spillover effect is found in cases where the patina of science is presented as science but without foundation.11 Thus, post-conviction analysis is often weighed down by misleading and ultimately incredible evidence.

Moreover, the progress of fire science has established markers and timelines for evaluating the reasonableness of expert evidence. Depending on the level of scientific knowledge at the time of trial (or plea) or developments since the conviction, different routes for relief might be available.

New Science as New Evidence

Seven editions of NFPA 921, beginning in 1992, and the publication of “Fire and Arson Scene Evidence” by the Department of Justice in 2000, have embraced the scientific methodology of fire investigation. Thus, constructing a timeline of forensic scientific developments can provide a clear guide for identifying “newly discovered” evidence that can be equated with “new knowledge.”12

Of course, the more developed the scientific explanation as an alternate theory, the greater its potential as newly discovered evidence.13

The state of fire science registers at two points in a criminal prosecution: (1) investigative and scientific methods known or knowable at the time of trial; and (2) developments in new science and techniques that emerge after conviction.

Depending on what was known about forensics at a particular time and how it was used or ignored, post-conviction claims can introduce newly discovered scientific evidence14 along with constitutional errors.15

For instance, new knowledge about the behavior of propane gas was critical to contradicting an outmoded and misleading conclusion of arson a decade earlier.

In 1995, the defendant in People v. Chase, 8 Misc. 3d 1016A (Wash. County Ct. 2005), had been convicted of arson involving three different fires. Eventually, he filed a CPL 440 motion based on newly discovered evidence among other issues. Specifically, he contested the evidence in the 1993 home fire in which the prosecution claimed he had loosened a propane gas hose from a 100-pound tank in the basement.

According to a prosecution witness, the fire damage pointed to the kitchen on the second or middle floor of the house as the source. To conform the indictment to the trial testimony, the prosecutor put forward a theory that propane gas pooled in the basement before spilling over to the next floor where it was ignited.

Defendant’s post-conviction motion included affidavits from three experts, two of whom appeared at a hearing refuting the prosecution’s theory:

They testified that recent scientific discoveries regarding the nature of propane made after 1995…disprove the keystone of the prosecution’s proof. Contrary to accepted scientific beliefs held at the time of the trial, when discharged in open air, propane does not settle to the floor. It does not act like water in a bathtub. Rather, a jet of propane would immediately and readily mix with the air around it. The air would dilute the gas rendering it non-combustible except in very limited and specific conditions, none of which were proven at the trial.

Another significant development since 1995 was a propane tank (20 pounds) product recall by the Consumer Products Safety Commission (CPSC) because they were “prone to rupture if unintentionally overfilled while cold, then warmed.” As a result, the propane would expand until it caused a “boiling liquid expanding vapor explosion.” And Chase’s experts testified that the 1993 fire fit the pattern of such an explosion. Additional expert evidence was introduced to show that new research on the behavior of propane gas was responsible for changes in safety regulations and guidelines for handling tanks.

The court vacated the judgment and ordered a new trial principally based on these scientific and engineering revelations.

Newly discovered evidence entails some kind of post-conviction investigation. In the Third Circuit decision, Lee v. Glunt, 667 F.3d 397 (3d Cir. 2012), the court granted discovery in a federal habeas corpus action for the purpose of developing new expert analysis.

Lee had been convicted of arson in 1990 (pre-NFPA 921). He pursued challenges in state court based on new science with due diligence, but his requests for discovery to facilitate expert analysis were denied. Thus, his state claims were not barred from federal review under Cullen v. Pinholster, 131 S.Ct. 1388 (2011).16

Indeed, the Third Circuit found that Lee’s petition addressed the “fundamental fairness” of his trial:

If Lee’s expert’s independent analysis of the fire scene evidence—applying principles from new developments in fire science—shows that the fire expert testimony at Lee’s trial was fundamentally unreliable, then Lee will be entitled to federal habeas relief on his due process claim.17

Post-Conviction ‘Brady’

The Indiana Court of Appeals confronted due process challenges in Bunch v. State, 964 N.E.2d 274 (Ct. App. Ind. 2012), when it reviewed a felony murder conviction involving a fire that occurred in 1995. The prosecution’s case heavily relied on cause-and-origin expert evidence, ATF laboratory analysis and a pathologist’s testimony about the rate of smoke inhalation.

The petitioner raised claims about the expert testimony based on new science, i.e., fire victim toxicology, fire investigation techniques, and prosecutorial and defense practices (such as a Brady violation or ineffectiveness of defense counsel).

The appeals court found that advances in toxicology analysis, which in 2001 were incorporated in NFPA 921, undermined the prosecution’s theory. This new interpretation or explanation for carbon monoxide saturation levels in the victim was a “transformative advancement” that revised the original portrayal of how the fire started and spread.

Indeed, as the amicus curiae submitted by the Innocence Network indicated, several states (Arizona, Nebraska and Oklahoma) had passed resolutions acknowledging the emergence of new science in arson investigation and the need for post-conviction review.18

The second point that the court reached concerned the prosecution’s failure to turn over an ATF report about the laboratory analysis. After trial, petitioner had subpoenaed her ATF file and uncovered significant exculpatory information. This undisclosed material contradicted the prosecution expert’s testimony about the presence of heavy petroleum distillate in one of the crucial samples.

Together, the newly discovered toxicology evidence and the Brady violation were enough to justify a new trial.


Science can strip away incendiary intent and transform a judgment of arson into an accident or act of nature. It can make evidence of guilt into newly discovered proof of innocence. It is the functional equivalent of an expert recanting their conclusion based on new research.19 And short of an actual recantation, the post-conviction affidavit of a defense expert and a timeline literature review might suffice to open the courthouse door.

First impressions can be misimpressions. And justice will not honor intuition over science.20 In the case of arson, the art of investigation must yield to the principles of causation.

Ken Strutin is director of legal information services at the New York State Defenders Association.


1. See “Strengthening Forensic Science in the United States: A Path Forward” (Nat’l Res. Council 2009) at 170-73.

2. See Ken Strutin, “Arson and the Science of Fire,”, Nov. 12, 2012.

3. See generally New York State Library standards collection.

4. See John J. Lentini, “Standard of Care in Fire Investigation” (2007).

5. John J. Lentini, “The Evolution of Fire Investigation, 1977-2011″ (2012) at 7.

6. Rivers, 18 N.Y.3d at 227.

7. See, e.g., United States v. Glynn, 578 F. Supp. 2d 567, 570 (S.D.N.Y. 2008) (ballistics match testimony changed from “absolute certainty” to “more likely than not”). See generally Bonnie Lanigan, “Firearms Identification: The Need for a Critical Approach to, and Possible Guidelines for, the Admissibility of ‘Ballistics’ Evidence,” 17 Suffolk J. Trial & App. Adv. 54 (2012).

8. See Caitlin Plummer and Imran Syed, “‘Shifted Science’ and Post-Conviction Relief,” 8 Stan. J.C.R. & C.L. 259, 274 n.67 (2012).

9. Schlesinger, 2012 U.S. Dist. LEXIS 15754 at 39; see also Allstate Ins. v. Gonyo, 2009 U.S. Dist. LEXIS 36597, 22-23 (N.D.N.Y April 29, 2009).

10. See Souliotes v. Hedgpeth, 2012 U.S. Dist. LEXIS 58689 at 139 (E.D. Cal. April 26, 2012) (cause-and-origin leads ignored). See generally Keith A. Findley & Michael S. Scott, “The Multiple Dimensions of Tunnel Vision in Criminal Cases,” 2006 Wis. L. Rev. 291.

11. See, e.g., United States v. Hebshie, 754 F. Supp. 2d 89, 115-20 (D. Mass. 2010) (canine acceleration detection criticized); Santos v. State Farm Fire & Cas., 28 Misc. 3d 1078, 1083 (Sup. Ct. Nassau County 2010) (computer fire modeling rejected).

12. See Marc Price Wolf, “Habeas Relief from Bad Science: Does Federal Habeas Corpus Provide Relief for Prisoners Possibly Convicted on Misunderstood Fire Science?,” 10 Minn. J.L. Sci. & Tech. 213, 239-42 (2009).

13. See John J. Lentini, “The Mythology of Arson Investigation” (2006); see also John J. Lentini, “‘Progress’ in Fire Investigation: Moving From Witchcraft and Folklore to the Misuse of Models and the Abuse of Science” (2010).

14. See, e.g., State v. Edmunds, 308 Wis. 2d 374 (Wis. Ct. App. 2008) (shaken baby syndrome “shift in mainstream medical opinion” as newly discovered evidence).

15. See “Shifted Science,” 8 Stan. J.C.R. & C.L. at 289-97.

16. See generally Samuel R. Wiseman, “Habeas After Pinholster,” 53 B.C.L. Rev. 953 (2012).

17. Lee, 667 F.3d at 407-08.

18. Bunch, 964 N.E.2d at 288; see also Iowa State Fire Marshal Implements Policy Changes to Prevent Wrongful Arson Convictions, Innocence Proj. Press Rel., July 7, 2011.

19. See, e.g., Ex parte Henderson, 2012 Tex. Crim. App. LEXIS 1605 (Ct. Crim. App. Tex. Dec. 5, 2012) (shaken baby syndrome); In re Richards, 2012 Cal. LEXIS 11005 (Cal. Dec. 3, 2012) (bite-mark evidence).

20. See Report of the Texas Forensic Science Commission: Willingham/Willis Investigation (April 15, 2011) (17 recommendations for improving arson investigations, at pp. 39-52).