Background: Scientific Standards for Arson Investigation


For generations, fire investigators used unscientific methods for determining whether fires were intentionally set. The nation’s leading standard-setting organization for fire science, the National Fire Protection Association, began developing clear standards in this area in the 1980s – and published scientific guidelines in 1992 (before Cameron Todd Willingham’s trial).


— The National Fire Protection Association (NFPA) Standards Council forms a Technical Committee for Fire Investigation (TCFI), charged with developing NFPA guidelines for investigating fires.  


— TCFI begins to develop NFPA 921, soliciting input from experts and practitioners nationwide.

Jan. 1992

— Original edition of NFPA 921 is published with “basic chapters for a fire investigation,” which make clear that the methodology to use is the scientific method (meaning investigators should not rely on techniques that have not been tested for scientific validity).

Jan. 1995

— The second edition of NFPA 921 is published with a chapter on “Incendiary Fires.” The legal community begins challenging fire investigators based upon NFPA 921 principles, while arson associations differ on how much to use it. (The International Association of Arson Investigators says, “It is only a guide.  It is not a standard,” while National Association of Fire Investigators embrace NFPA 921 and begin to teach the science and methodology described.)

Jan. 1998

— Third edition of NFPA 921 is published. There is still some disagreement about it within the fire investigation field, but a growing number of court cases cite it.  

June 2000

— The U.S. Dept. of Justice’s National Institute of Justice publishes a guide referring to NFPA 921 as “a consensus document reflecting the knowledge and experience of fire, engineering, legal, and investigative experts across the United States.”  The NIJ document, “Fire and Arson Scene Evidence: a Guide for Public Safety Personnel,” notes that NFPA 921 is continuously reviewed, public proposals and comments are solicited, and a revised edition is produced every three to five years.  NIJ says that NFPA 921 has become a “benchmark for the training and expertise of everyone who purports to be an expert in the origin and cause determination of fires.”

Jan. 2001

— Fourth edition of NFPA 921 is published. The International Association of Arson Investigators (while questioning the use of the term “scientific” in the document because its members may not have scientific skill sets) had embraced the scientific approach to fire investigation embodied in NFPA 921 in 2000.

Jan. 2004

— Fifth edition of NFPA 921 is published. Language is added to say that ignitable liquid pattern recognition cannot be done to a sufficient level of certainty unless there are confirming lab results.

Dec. 2008

— Sixth edition of NFPA 921 is published.

Embraced by the Profession

The National Association of Fire Investigators (NAFI) was founded in 1961 and is the nation’s leading professional membership organization working to ensure that fire investigation is based on solid science. NAFI’s official position is that NFPA 921 is the standard to which all fire and explosion investigations should be held by the courts and the profession.  NAFI believes that NFPA 921 is the professional standard of care for fire and explosion investigation as the only peer-reviewed, science-based, consensus text on fire investigation.

The National Certification Board Certified Fire and Explosion Investigator examination has been based upon the investigative principles in 921 since 1987, even before the official adoption of the document by the NFPA.

In 2000, the International Association of Arson Investigators’ then-president, Gerard Naylis, began urging the membership to adopt NFPA 921.  This was the IAAI’s first formal endorsement of the document. Naylis said, “It’s time for the IAAI to stop looking in the rear view mirror and start looking out the windshield.”  IAAI now publishes a User’s Manual to NFPA 921.

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