Fire investigations have been going on for centuries. We all recall historical references of these investigations, from Nero's burning of Rome to Mrs. O'Leary's cow.  Over the years, the art and craft of the fire investigator has incorporated many techniques and applications.

In 1992, NFPA 921-Guidelines for Fire Investigations was published.  The publication's intent was to define standards of competence related to fire investigations, which it generally has.  It is doubtful, however, that the intent was to stir up controversy—but it has.

Much of the controversy has revolved around the ultimate purpose. Although titled and labeled as a guideline, several courts have ruled that it is a standard.  This distinction changes the outlook from a "should" to a "must" document, and many expert opinions have been overturned because the guideline was not rigorously followed. 

Another issue is that several long-standing beliefs concerning the appearance of fire scenes are challenged as being scientifically uncertain, which then opens the door to challenges to any finding that can't be produced in the lab.  Since 1992, many court cases have occurred, and the 2004 edition of NFPA 921 has added information to aid fire investigators.

Although only a small percentage of fire investigations will ever arrive in the courtroom, we must treat each one as the next famous case.  With that in mind, the proper application of NFPA 921 becomes paramount.

The proper application starts with complete familiarity with the content, as well as acceptance of it as an authoritative document.  Lip service will not do.  The scientific method must then be applied to the investigation, consisting of:

  • Defining the problem
  • Collecting data
  • Formulating a hypothesis
  • Testing that hypothesis
  • Revising the hypothesis and finalize
  • Reporting on the final conclusion
  • The investigator must also be prepared to justify all steps taken, as well as the reasons that some steps were not taken.

So how does a fire investigator proceed?

Let’s look at the flow of a case suspected to be electrical.  The steps will be very similar for mechanical and other causes.

The first step is to determine the area of origin by examining the exterior and interior, and then locating the area of most damage.

The second step is to determine the point of origin by examining micro burn patterns and determining if there is an electrical source in the area such as outlets, TV jacks, or wiring.  Are there remains of outlet boxes, yokes, or screws, and has the power been disconnected?

The third step is to observe the point of origin and evidence in detail; for example, by looking at what components were destroyed by heat or if there is pitting on the underside of the binding screws or base plate.  At this point, rule out other causes in the area and other points of origin.

The fourth step is to examine the system, including the meter and masthead, overhead wires, the circuit panel, and breakers.  Now, trace the point of origin to the panel.

If the point of origin was at outlet #8 in the dining room, trace it to the panel to determine if the breaker tripped.  Next, obtain the best history by talking to the owner about any problems or recently performed work.

The last step is to determine the cause and test the hypothesis.

Key points throughout the investigation are:

  • Do not touch - major cause of spoliation
  • Use common sense
  • Take photos and measurements, get product data, meter readings, etc.
  • If needed, retain the help other experts
  • Tag the evidence and do not tamper
  • If possible, secure the scene
  • Make sure all other parties are notified (electrical contractor, general contractor, product manufacturer, etc.)

The conduct of sound fire investigations in accordance with NFPA 921 will provide the objective evidence needed for legally sound decisions.

The April 2001 edition of the Investigative Engineer also discussed Fire Investigations and the Scientific Method. This article is located under the "Fire Origin and Cause" category of the PIE article website.

Copyright 2004 Professional Investigative Engineers. All rights reserved.