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“Arson investigation is very slow, tedious, dirty work.”

- Mike Morgan

Chapter 17Arson and Explosion Investigations

▪ Fire: type of oxidation, which is a combination of

oxygen with other substances to produce new

substances.

▪ Arson: crime of maliciously, voluntarily and

willfully setting fire to an object.

– To start a fire: the minimum temperature needed

to spontaneously ignite fuel must be reached.

What is Fire and Arson?

▪ 82% white and 92% male

▪ Over 50% were 27 or younger

▪ 31 fires set on average

▪ 87% prior felony arrests

▪ 2/3rds average or above intelligence; however, 90%

had high school or less

▪ 25% history of suicide attempt and 50% history of

psychological problems

▪ Many had unloving relationships with parents

▪ Most reported watching the blaze

Arsonist Typologies

Chris Hartley arrested for

30 South Carolina

forest fires

▪ Thomas A. Sweatt was arrested

and charged with 11 federal

offenses stemming from four fires

and an attempted arson in

Maryland and DC.

▪ Sweatt was tied to the crimes through DNA taken from

items (pair of pants left near a house and a sock that

apparently was used as a wick).

Serial Arsonist

Video: Mind of the Serial Arsonist

▪ Arson investigator: begins examining a fire

scene for signs of arson as soon as the fire has

been extinguished.

– Can start before a search warrant is obtained.

– Most are started with petroleum-based

accelerants.

▪ The search: focus on finding the

fire’s origin, which may point to the

accelerant or ignition device.

Searching the Fire Scene

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Video: Arson Fire Investigators

▪ Telltale signs of arson:

– evidence of separate and

unconnected fires

– the use of “streamers” to

spread the fire from one area to another

– evidence of severe burning found on the floor as

opposed to the ceiling of a structure

▪ Direction of fire: tendency to move in an upward

direction, and origin will likely be the lowest point

showing the most intense characteristics of burning.

Searching the Fire Scene

Flammable liquid trailer

▪ Items to be collected:

– ash and soot

– porous materials which may contain accelerant

– traces of flammable liquid residues (vapor detector)

– igniters (matches, sparking device or parts of

“Molotov cocktail”)

▪ Storage: stored in airtight containers,

leaving an airspace to remove samples

Collection of Fire Evidence Video: Photo Ionization Detector

▪ Gas chromatography: most sensitive and

reliable instrument for detecting and

characterizing flammable residues.

– Majority are initiated by gasoline and kerosene.

– Produces a chromatographic

pattern of a particular petroleum

product.

Analysis of Fire Evidence

▪ After departing from JFK airport, TWA

Flight 800 exploded mid-air 12 minutes

into the flight.

▪ 230 people were killed and aircraft was

destroyed.

▪ There was much speculation centered

on the crash being a terrorist attack.

▪ In 2000, they concluded that the

probable cause of the accident was “an

explosion of the center wing fuel tank”.

TWA Flight 800

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Video: TWA Flight 800

▪ Explosion: a chemical or mechanical action

resulting in the rapid expansion of gases.

– The sudden buildup of gas pressure constitutes

the nature of an explosion.

– Explosives are classified as high or

low depending upon the speed

at which they decompose.

▪ Eric Rudolf was convicted of Atlanta

Olympics and abortion clinic bombings

What is an Explosion?

▪ Low explosives: most widely used

– Black powder: is a mixture of potassium or

sodium nitrate, charcoal, and sulfur.

– Smokeless powder: consists of nitrated cotton

(nitrocellulose) or nitroglycerin and nitrocellulose.

Types of Explosives

Ted Kaczynski constructed bombs

containing smokeless explosive

powders and a box, and the plugs that

sealed the pipe ends were hand crafted

from wood.

▪ Published in 1971 by William Powell during his high school

and college years in protest of the Vietnam War

▪ His research came from military and special forces manuals

in New York Cities public libraries

▪ Central theme was violence is an acceptable means to bring

about political change

▪ Provides recipes for manufacturing explosive

devices and telecommunications jamming

devices using common household items

▪ After second thoughts, the publisher refused

Powell’s request to remove the book from

print

Homemade Explosives:

The Anarchist Cookbook

▪ High explosives

– Primary explosives: ultra-sensitive to heat, shock,

or friction and provide ingredients found in blasting

caps or primers.

– Secondary explosives: relatively insensitive to heat,

shock, or friction and will burn rather than detonate

if ignited in small quantities in the open air.

– Examples: commercial and military

blasting (dynamite, TNT, PETN, RDX)

Types of Explosives Types of Explosives

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▪ U.S.: nitroglycerin-based dynamite has

disappeared from the market.

– Replaced by ammonium nitrate-based explosives

(i.e., water gels, emulsions and ANFO explosives)

▪ Outside U.S.: accessibility of military high

explosives to terrorist organizations

– RDX is the most popular and powerful of the military

explosives, often encountered in the form of pliable

plastic known as C-4.

The Explosive Market

▪ The bomb site must be systematically searched to

recover any trace of a detonating mechanism or any

other foreign items.

– Objects located at or near the origin of the explosion

must be collected.

– Often a crater is located at the origin and loose soil

and other debris must be preserved from its interior.

Searching for Explosive Evidence

▪ Materials collected must be placed in sealed air-

tight containers and labeled.

▪ Items collected from different areas are

packaged in separate containers.

▪ Why airtight containers? Some explosives can

diffuse through plastic and contaminate nearby

containers.

Collection of Explosive Evidence

▪ Law enforcement

commonly use

specially equipped

robots to search and

collect explosives and

evidence.

▪ The sophistication of

bombs makes the use

of robots an important

safety tool and as a

result saves lives.

Collection of Explosive Evidence

“Robots”

▪ The FBI Futures Working Group is a collaboration

between the FBI and the Society of Police Futurists

International.

▪ They provide national and international law

enforcement with information related to future

forecasting.

▪ In the past year and based on international terrorism

data, they predict it is only a matter of time before the

U.S. is the victim of suicide bombings.

▪ When that occurs, the challenges to forensic scientists

will be unprecedented.

Forensics Nightmare Video: Suicide Bomber

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▪ Ion mobility spectrometer (IMS): screening

objects for the presence of explosive residues.

– IMS is used for preliminary identification of an

explosive residue

– A confirmatory test must follow

▪ In the laboratory: debris collected will be examined

microscopically for unconsumed explosive particles.

▪ Recovered debris must be rinsed with organic

solvents and analyzed.

Analysis of Explosive Evidence

Circuit board fragment found in cargo

hold of plane bombing

▪ Two Types:

– Detection: detects presence of a bomb (e.g., airport

screening tests of luggage)

– Identification: helps police find suspects after detonation

▪ Identification Taggants:

– Most commonly used are microscopic polymer particles

that can be identified after the explosion

– They provide information about the explosive and

manufacturers batch

– Records can lead to a specific store where explosives

were sold

Explosives Photo Lineup:

“Bomb Taggants”

Micro-taggant identification

particles

▪ The Oklahoma City bombing

was a domestic terrorist attack

on April 19, 1995.

▪ Aimed at the U.S. government in

the Alfred P. Murrah Federal

Building.

▪ The attack claimed 168 lives

and left over 800 people injured.

▪ Until the September 11, 2001

attacks, it was the deadliest act

of terrorism on U.S. soil.

Oklahoma City

▪ From the mid-1980’s to the

early 90’s, dozens of retail

businesses were bursting

into flames.

▪ Nova trails along with fire

detectives as they try to

crack the case of a serial

arsonist.

Video: Hunt for a Serial Arsonist