Transcript Analysis of Explosives

Analysis of Explosives
Ms. Scribner’s Forensic Science
Class—Eisenhower High School
Introduction
 Most bombing incidents involve
homemade explosive devices
 There are a great many types of
explosives and explosive devices
 Lab must determine type of explosives
and, if possible, reconstruct the
explosive device
Explosives
 Combustion (or decomposition) of
explosives occurs so rapidly, that there
isn’t enough time for the oxygen in the
surrounding atmosphere to combine
with the fuel.
 Therefore, many explosives must have
their own source of oxygen – or
oxidizing agents
Definitions
 Explosion—sudden release of
chemical or mechanical energy caused
by an oxidation or decomposition
reaction that produces heat and a rapid
expansion of gases.
Definitions
 Reagent—a substance used to produce
a chemical reaction to detect, measure,
or produce other substances.
 Spot tests can be
administered to
identify
IED--An improvised
explosive device is a bomb constructed and
deployed in ways other than in conventional
military action. It may be constructed of
conventional military explosives, such as an
artillery round, attached to a detonating
mechanism. IEDs are commonly used as
roadside bombs.
Chemistry of Explosion
 Essentially a combustion
reaction - like a fire
 Major difference is speed of
reaction
 Damage caused by rapidly
escaping gases and
confinement
Definitions
 High explosives—chemicals that oxidize
extremely rapidly, producing heat, light
and a shock wave; will explode even if
not confined
 Low explosives—chemicals that oxidize
rapidly, producing heat, light, and a
pressure wave; will explode only when
confined.
Types of Explosives
 Low explosives
• Escaping gases up to about 3000fps (foot per
second)
• Crucial element is physical mixture of oxygen and
fuel
• Examples are black and smokeless powders
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Black powder is mixture of potassium nitrate, charcoal
and sulfur
Smokeless powder is nitrocellulose and perhaps
nitroglycerine
Types of Explosives
 High explosives
•
Velocity of escaping gases up to 10,000fps
• Oxygen usually contained infuel molecule

Two types
• Initiating - Senistive, will detonate readily when
subjected to heat or shock. Used to detonate other
explosives in explosive train
• Noninitiating - relatively insensitive, requires heat or
shock. Includes TNT or PETN
Classification by Use
 Commerical Explosions: Ammonium
Nitrate fuel oil (ANFO), black powder,
dynamite
 Military Explosions: RDX (commonly
known as C-4), PETN, PETN mixed
with TNT to make grenades
 IED—low explosives placed into
confinded containers
Ammonium nitrate based
•
Water gels
• Emulsions--are intimate mixtures of oxidizers
and carbonaceous fuels made as water in oil type
of Emulsions used for blasting in quarries,
stripping in underground metal mines, tunneling,
well sinking, and road construction .
•
ANFO’s--ammonium
nitrate/fuel oil) is a widely used
bulk industrial explosive mixture
Analysis of Explosives
 Microscopy
 Thin layer chromatography
•
Visualise with Greiss reagents
 Infrared spectrophotometry
 Detonator fragments
Microscopic Examination
 Perforated disc
 Tube
 Ball
 Disc
 Rod
 Lamel
1, 2, and 3 step Explosive Trains
Explosive Trains
The Role of Forensic Science
in the Investigation of Major
Acts of Terrorism
 A forensic science technician, also
referred to as a criminalist, gathers,
interprets and analyzes evidence using
forensic science techniques and tests.
 Analyze and test tissue samples
 Test chemical substances and physical materials
 Interpret lab findings
 Collect criminal evidence
 Reconstruct crime scenes
 Testify as expert witness during trials
First World Trade
Center Bombing
1993 The Scenario—first bombing attempt
 Urea nitrate bomb put into truck and driven
into underground WTC garage and parked at
4th level down
 Subsequent explosion did extensive damage
to several levels of the garage and less
damage to other levels
 Although goal was to topple WTC, little
structural damage was done
 Some loss of life
Goals of Investigation
 Identify victims
 Identify explosive
 Recover bomb and timing
device
 Determine method of delivery
Evidence Sought
 Investigators had to remove large
quantities of concrete, steel and cars to
get to bomb seat
 Bomb seat contained most of the
important evidence
 Bomb parts; timer, casing, etc.
 Explosive residue
 Parts of truck that contained explosive
Areas of Forensic Science
 Explosives
 Engineering
 Questioned documents
 Fingerprints
 Pathology
 DNA
The Murrah Building,
Oklahoma City
Domestic Terrorism
The Scenario--1995
 ANFO explosive and timer
packed into a rented truck,
which was then parked
outside Murrah building
 Explosive confined to
closed space such as truck
is much more powerful
 Resulting explosion
resulted in severe damage
to building and loss of
more than 100 lives
Goals of Investigation
 Identify victims
 Identify explosive
 Find timer and
bomb parts
 Determine method
of delivery
Evidence Sought
 Easier to find than in WTC because
bomb seat outside building
 Explosive residues
 Bomb parts
 Bodies and body parts; cadaver dogs,
flies
 Personal effects; helps in identification
of human remains
Areas of Forensic Science
 Anthropology
 DNA and serology
 Pathology
 Entomology
 Explosives
 Trace evidence
 Engineering
 Questioned documents
 Fingerprints
WTC Destruction-2001
The Scenario
 Large airplanes, loaded with fuel, crash into
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WTC buildings
Raging fires ignite everything in building
above crash sites.
Metal supports melt from heat
Building collapses due to inability to support
its own weight after structural damage
Thousands of people killed
 http://www.history.com/topics/9-11-attacks
4min video
Goals of Investigation
 Cause known, no need to determine
how destruction occurred
 Recover and identify bodies, parts of
bodies and charred remains
 Recover personal effects that might
help identify victims or perpetrators
 Evidence that might determine how
hijackings occurred.
Evidence Sought
 Bodies and body parts; cadaver dogs,
flies
 Charred remains
 Personal effects
 Trace evidence such as charred papers
 Weapons such as knives
 Constraining devices such as wire
Areas of Forensic Science
 Anthropology
 DNA and serology
 Odontology
 Pathology
 Entomology
 Trace evidence
 Questioned documents
 Fingerprints
 Tools and toolmarks
Boston Bombing—April 15, 2013
 Two pressure cooker bombs exploded
during the Boston Marathon at 2:49 pm
killing 3 people and injuring an estimated
264 others. The bombs exploded about
12 seconds and 210 yards (190 m) apart,
near the finish line on Boylston Street
 A pressure cooker bomb is
an The IED was created by
inserting explosive material into a
pressure cooker and attaching a
blasting cap into the cover of the
cooker.
 Pressure cooker bombs have been
used in a number of attacks--2006 Mumbai train bombings, 2010
Stockholm bombing (failed to
explode), 2010 Times Spare car
bombing attempt (failed to explode)
Goals of Investigation
 Cause known, no need to determine
how destruction occurred
 Recover and identify bodies, parts of
bodies and charred remains
 Recover personal effects that might
help identify victims or perpetrators
 Evidence that might determine how the
object was left at the scene.
Evidence Sought
 Photos of person of interest
 Personal effects
 Bomb parts; timer, casing, etc.
 Explosive residue
 Constraining devices such as pieces of
the pressure cooker, wire or duct tape
Areas of Forensic Science
 Anthropology
 DNA and serology
 Odontology
 Pathology
 Entomology
 Trace evidence
 Questioned documents
 Fingerprints
 Tools and toolmarks