Where there were some that wanted the Level of Certainty section removed from NFPA 921, it appears that the present judgement was to retitle the section and update the wording.

The new title for the section being suggested by the committee is “Expression of Certainty.” The wording for that section states, “Someone may express an opinion to a higher or lower level of certainty. The expression is determined by the investigator’s confidence in the data, in the analysis of that data, and testing of the hypotheses formed.” This wording also conforms to the recommendations of the DOJ. Under Expressions of Certainty, the document continues to give the user definitions for the words “probable” and “possible” that can be used as a level of certainty. Probable being an expression corresponding to being more likely than not. Possible being an expression that the hypothesis may be demonstrated to be feasible but cannot be either ruled out or declared probable. This expression is used if there is more than one hypothesis that remains at the end of the investigation. In addition to this information the document defines want is fire investigation certainty. It states, “Fire investigators achieve reasonable fire investigation certainty when they have properly applied all of the steps of the scientific method to reach a unique and reliable final hypothesis.”

Because there has been no suggestion as to acceptable wording, other than what is found in NFPA 921, it is suggested that everyone develop wording based on the guidance found in NFPA 921. If the new wording is approved by the membership of the National Fire Protection Association, then the user of the wording and guidance found in NFPA 921 can be said to be a conscience of not only the fire investigation community that follows that organization’s guidance, but that of the entire fire protection community that are members of that organization. This should address the original concerns of NCFS.

Jim Mazerat
Forensic Investigations Group