Written by Dr. Mukesh Sharma & Dr. Ajay Sharma
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.
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
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:
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
Step 2Fire scene examination and information collectionThe 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.
Information summary, induction, and analysisInductive reasoning with all of the
collected and observed information should be done in a defined manner.
Develop hypothesis and verifyOn 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 5Final report or opinionAll 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.
Case StudyA 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.
Observations1) 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
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
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.
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.
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.
ResultsOur 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.
DiscussionIn 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.
ConclusionIn 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.
SummaryDuring 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 AuthorsDr. 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
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.
References1. 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.
4. DeHaan, J. 1991. Kirk's Fire Investigation.
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
9. Please refer to
Photos 1 – 9.