Forensic Investigation in Fire & Arson Cases
Written by Dr. Mukesh Sharma & Dr. Ajay Sharma   

This article appeared in the May-June 2020 issue of Evidence Technology Magazine.
You can view that issue here.

FORENSIC SCIENCE IS A DIVERSE, interdisciplinary field that is rapidly expanding in terms of public interest and importance in the administration of justice. The word arson comes from the Latin ardere, meaning “to burn.” The willful setting of fires has been a recognized crime for thousands of years. This report takes a look at utilizing fire scene evidence when solving arson and fire crimes.

Fire investigation can be performed in two stages. The first involves examination of the fire scene to determine the cause of the fire, its origin, and the development/spread of the fire. The second stage involves laboratory analysis of samples recovered from a fire scene, normally when arson is suspected1,2.

This article is divided into two sections: The first part deals with the basic methodology which is to be adopted during the investigation of a fire; and the second part features a case study with photographs. The purpose of this report is to give a brief and relatively simplistic approach to the investigation of fire/arson cases.

The investigation of fires or arson is an act as well as a science. The gathering of factual information, as well as the analysis of those facts, must be accomplished objectively and truthfully. The systematic approach recommended follows the scientific method used in the physical sciences3. The flow chart shown below (Figure 1), which is a result of thorough study of the reference literature4,5, is developed to assist the investigator in examining the fire crime scene in five steps. These are explained as:

Step 1
Theoretical analysis, or “case study”

The investigator should have knowledge of fire dynamics, and understand which factors aid in the development and spread of a fire.


Step 2
Fire scene examination and information collection

The crime scene investigator (CSI) makes observations at the crime scene for details such as char pattern, color of smoke, color of flame, and residue parts.

Step 3
Information summary, induction, and analysis

Inductive reasoning with all of the collected and observed information should be done in a defined manner.

Step 4
Develop hypothesis and verify

On the basis of the data analysis, the CSI should develop a hypothesis to explain the origin and cause of fire, and then test the hypothesis. In other words, make assumptions and then verify.


Step 5
Final report or opinion

All the collected and observed information and evidence are forwarded for laboratory examination. This will contribute to the conclusive report about the occurrence at the scene.

Figure 1: Flow chart for analyzing a fire/arson investigation, amended form of earlier publications6

Case Study
A police chowki (Editor's Note: a chowki is a sub police station) in Bharatpur, Rajasthan, India was found burned due to unknown reasons, and the investigating agency suspected that the police official appointed at the chowki was misguiding the investigation. The authors visited the site in order to provide direction to the investigating agency; offer guidance for the laboratory examination of the debris and wires; and offer a final opinion in the case.

1) Images 1 – 4 show the burned cabin of the chowki and an area of burned grass outside the cabin; a melted bedframe; and other charred material. Inside the chowki, the whole room was heat-affected, and some firearms were also found completely burned. These burned firearms and ammunition contributed to some confusion during the initial investigation. The area where the radio was installed was completely heat-affected and burned.

Image 1

Image 2

Image 3

Image 4

Images 1 – 4: Interior and exterior of the chowki

2) The switch of the radio was found completely melted and burned, which verified the level of heat during fire.

Image 5: Melted switch inside the chowki

3) After thoroughly searching the nearby area, one aluminum pot generally used for boiling water and preparing tea was found. It was melted from the bottom, with a pattern of circular lines.

Image 6: Near the chowki area, a melted aluminum pot was found.

4) In the charred grass and nearby burned material, we found two heating plates, generally used for boiling water and tea preparation. One plate was intact with its copper wire. The second plate was found broken, with some foreign material melted and adhered to the copper. We concluded that the heating plate, used to heat the empty aluminum pan, caused the bottom of the aluminum pan to melt. The melted aluminum dripped onto the coil on the heating plate, causing a short-circuit and fire.

Image 7

Image 8

Images 7 – 8: Copper-based heating coils. The first copper coil was intact. The other one was damaged, along with some foreign material adhered to it.

5) The heating coil was connected to the main power supply with aluminum wire. These connected wires were found melted not far from the location of the heating coil. Globules were also observed on the aluminum wire.

Image 9: Globules can be seen on the aluminum connecting wire, which was used to connect the coil to the power supply.

Our investigation proved the burned police chowki was the result of a fire, due to negligence, and not the result of arson or any type of explosion. The composition of the aluminum pan, the aluminum pan collected on the heating plate, and the aluminum wire on the heating plate were compared using chemical testing, specific gravity, and impurity tests (trace element analysis). To properly analyze elemental composition testing, X-ray fluorescence (XRF) is suggested. On the basis of the observations in the laboratory, we concluded that the aluminum pan and melted materials are similar. Through the forensic investigation, the case was solved. As a result of the authors’ report, three staff of the police chowki were suspended for negligence while on duty.

In some cases of fire, external heating involves the wire or wired device as the “victim” of fire, and not as the initiator of fire. But some situations do exist where external heating of wiring serves as the initiating event. In many cases, arcing occurs after sufficient overheating. The NFPA 921: Guide for Fire and Explosion Investigations (2004)7, provides photographic examples of wires with parting arcs, but it includes no metallurgical investigation. A parting arc, in this case, would have occurred after the fire had started, as the hot, energized wire was pulled apart. The arc was not considered to be the cause of the fire because of its short duration, but it was evidence for flowing current.

Careful examination of the insulation tells the truth of internal or external heating of the metallic conductor. Experiments were conducted in our laboratory to study the effects of heat on insulation. The melting point of the aluminum pot is quite high. We also ruled out the possibility of explosion and burning due to the firearms or ammunition, on the basis of our finding that the initiation of the fire was from the outside, and only after being exposed to heat did the ammunition kept in the police chowki actually burn.

In 1974, the author of a textbook on electrical insulation8 wrote: “The fundamental breakdown processes are not understood; not for lack of experimental observations but because our background knowledge is too crude.” Unfortunately, even today this statement remains true with regards to wiring and wired devices in buildings.

In the case described here, on the basis of observations made at the scene and the condition of the electrical wiring, the cause of the fire was an electric spark9 in the copper heating plate as it was being used to make tea.

During an investigation to determine the origin and cause of fire, evidence may be uncovered that indicates the fire was started due to an electric spark. These fires are often the result of natural curiosity and experimentation, while some are willfully and maliciously set for a variety of reasons. All fire incidents are different. But utilizing the methodology described here, CSIs can work toward reconstructing a fire/arson investigation.

About The Authors
Dr. Mukesh Sharma is the Assistant Director of the Physics Division of the State Forensic Science Lab in Jaipur, Rajasthan, India, where he has visited 623 crime scenes and reported 600 cases. He is a qualified expert in physics (M.S.), material science (Ph.D.), and psychology (M.S), with 12 years of experience in the field of forensic science and crime scene investigation. He has been awarded many times at the national and international level. He has published more than 135 research articles and eight books in various fields of physics and forensic sciences.

Dr. Ajay Sharma (M.S., Ph.D.) is posted as Additional Director and holds the position of Director of the State Forensic Science Laboratory in Jaipur, Rajasthan, India. He has 30 years’ experience in the field of forensic science. He has examined about 10,000 cases, and has been awarded best paper presentation at conferences organized by Ministry of Home Affairs, India in 2005, 2007, and 2009.

1. Kirk, P. 1974. Fire Investigation (2nd Ed). New York: John Wiley & Sons; also, Béland, B. 1984. Electrical damages—cause or consequence? J. Forensic Sciences. 29:747–61.

2. NFPA 921: Basic Methodology in Fire and Explosion Investigations. 1992. Boston; also, NFPA 921: Guide for Fire and Explosion Investigations. 2001. Quincy, MA.

3. Fire in the United States, 1985-1994 (9th Ed.). 1997. Emmitsburg, MD: U.S. Fire Administration.

4. DeHaan, J. 1991. Kirk's Fire Investigation. London: Prentice-Hall.

5. Phillips, C., and D. McFadeen. 1982. Investigating the Fireground. London: Prentice-Hall.

6. Dixit R., S. Jangir, P. Gupta, and M. Sharma. 2016. Unknowingly accident of fire: An expensive omission. J. Forensic Res. 6(314). doi: 10.4172/2157-7145.1000314

7. NFPA 921: Guide for Fire and Explosion Investigations. 2001. Quincy, MA.

8. Sillars, R.W. 1974. Electrical Insulating Materials and Their Application. London: Peter Peregrinus.

9. Please refer to Photos 1 – 9.


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