Arson is, of course, the intentional setting of a fire. Arson is determined ex post facto by a “fire investigator”. Fire investigators have historically been people who started their career with a fire department, and inherited the job from a predecessor. Training was largely “on the job” as a result of mentoring by superiors. It might also be common for novice fire inspectors to attend a one week training course. The body of knowledge concerning the causes, and locations of origin, of fires was anecdotal and passed from one generation of fire inspectors to another as folklore. Some have even compared the “old folklore science” of fire investigation to witchcraft.
I’m happy to report that true fire science has made great strides over the last two decades, and what it has determined is that most of the “rules of thumb” that were the “stock in trade” of fire investigators for decades were wrong.
Here is a short list of what fire investigators firmly, and wrongly, believed for decades were indicative of an intentional fire set with the use of an accelerant:
1) Burn patterns, or “pour” patterns on the floor.
2) Spalling of concrete.
3) “Alligatoring” or “checkering” of wood surfaces.
4) Crazed glass in windows.
5) Location and depth of char.
6) Holes burned in the floor.
7) Melted or annealed metal.
What was not understood at the time was the phenomenon of “flashover”. Flashover is when the temperature at the ceiling in a room (with a fire in it) reaches a level sufficient to cause spontaneous combustion of everything in the room. Once flashover has occured, all of the above “rules of thumb” are meaningless. To better understand what flashover is all about, here is a very illuminating video:
Note that it can take just a few minutes to go from a smoldering cigarette to flashover.
It wasn’t until the early 1990’s that science began understanding the phenomenon of flashover. And it wasn’t until 1992 when the (US) National Fire Protection Association (NFPA) published the first edition of its standard for fire investigation based upon scientific principles, NFPA 921: Guide for Fire and Explosion Investigations. At publication, the guide was embraced and adopted by the UK, but the reaction of the US fire inspection community was “wailing and moaning and gnashing of teeth”. Old-line fire inspectors resisted this mightily, and it has taken years for “921” to become generally accepted as the authoritative document, but it has happened.
However, despite the strides made by fire science, problems linger. In 2005, Steve Carman, Senior Special Agent ATF, helped design and conduct an experiment to judge the ability of experienced fire investigators to determine the location of origin of a fire. A test room was set on fire and allowed to burn for 7 minutes. 53 experienced fire investigators (who did not observe the fire) from both the public and private sectors were tasked with determining in which quadrant of the room the fire started. The results follow:
So you can see, we’re not completely “there” yet in the world of fire science. Steve Carman, has since retired from ATF, and now has his own fire investigation service, Carman and Associates in Sacramento, CA.
Now let me wax “editorial” a bit. I have no data, and this is speculation on my part, but I would venture a guess that “folklore fire science” has been responsible for more wrongful executions than any other area of forensics. You may have heard of Cameron Todd Willingham. “Todd” was convicted and subsequently executed for setting a fire that killed his three children in Corsicana, TX in 1991. He proclaimed his innocence to the end, and a post-execution investigation by renowned fire scientists, among them Dr. Gerald Hurst, determined that the fire was not arson. The state of Texas has refused to just come right out and admit they executed an innocent man. I have recently been involved in an arson death penalty case here in Ohio in which the conviction was based upon the testimony of a fire investigator who’d had a total of 6 days of training. My study of the evidence convinces me the defendant is innocent, and by the way, he’s been in prison for 21 years (so far), and his execution is pending.
I’m hopeful that the past and continuing advances of science will prevent further miscarriages of justice in future, but there are still lots of cases out there in which junk fire science has wrongfully imprisoned people, and in more than a few cases, sentenced them to death.
Here is some reference material for you:
1) John Lentini is a preeminent US fire scientist, and with his permission, here is his paper titled “The Mythology Of Arson Investigation”:
John can be reached at:John Lentini, CFI, D-ABC Scientific Fire Analysis, LLC 32836 Bimini Lane Big Pine Key, FL 33043
2) Also by John Lentini, and co-authored with Barry Scheck, co-founder of the Innocence Project is a presentation titled “Post Conviction Strategies in Arson Cases”. This is best consumed along with a presenter’s narrative, but there is a wealth of information in here (it’s a big file):
3) Here is a presentation from the Arson Research Project that deals specifically with burn pattern analysis in post-flashover fires: