Download Secondary explosives must be detonated by a primary explosive.

Chapter 14
FORENSIC INVESTIGATION
OF EXPLOSIONS
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-1
Unit Objectives
• Understand how explosives are classified
• List some common commercial,
homemade and military explosives.
• Describe how to collect physical evidence
at the scene of an explosion.
• Describe laboratory procedures used to
detect and identify explosive residues.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-2
Explosions
A chemical explosive is a compound or a
mixture of compounds which, when
subjected to heat, impact, friction, or shock,
undergoes very rapid, self-propagating,
heat- producing decomposition.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-3
Explosions
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-4
Shock Wave
• It is this sudden buildup of gas pressure that
constitutes the nature of an explosion.
• The speed at which explosives decompose
permits their classification as high or low
explosives.
• Video: Rocket fuel production plant shock
wave. http://www.youtube.com/watch?v=_KuGizBjDXo
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-5
Gunpowder
• The most widely used explosives in the lowexplosive group are black powder and
smokeless powder. Burn rate is less than 3000
ft/second
• Black powder is a mixture of potassium or
sodium nitrate, charcoal, and sulfur. Video
• Smokeless powder consists of nitrated cotton
(nitrocellulose) or nitroglycerin and
nitrocellulose. Video
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-6
Explosions
• Among the high explosives, primary explosives
are ultra-sensitive to heat, shock, or friction and
provide the major ingredients found in blasting
caps or primers used to detonate other explosives.
Examples are DDNP and lead azide. Web site
• Burn rates are 3000 –9000 ft/second.
Blasting Caps
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-7
DDNP
• DDNP, an acronym for diazodinitrophenol, is a
picric acid derivative with somewhat good
stability and explosive velocity. It is still
susceptible to heat, friction, and shock making
it a primary explosive. Its preparation is very
simple, needing only picramic acid, sodium or
potassium nitrite, and some dilute hydrochloric
or sulfuric acid. This compound was first
prepared by Dr. Griess in 1858, and this led
him to conduct ground breaking research on
the diazotization reaction.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-8
Secondary Explosives
• Secondary explosives are relatively insensitive
to heat, shock, or friction and will normally
burn rather than detonate if ignited in small
quantities in the open air. Dynamite & TNT,
PETN, RDX
Diagram of dynamite.
1. Sawdust soaked in
nitroglycerin.
2. Protective coating
surrounding the
explosive material.
3. Blasting cap.
4. Electrical cable (or
fuse) connected to the
blasting cap.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-9
Dynamite
• Dynamite is an explosive material based on
nitroglycern, initially using diatomaceous earth or
another absorbent substance such as powdered
shells, clay, sawdust, or wood pulp. Dynamite was
invented by the Swedish chemist Alfred Nobel
1867. Remember Nobel Prizes?
• Dynamite is usually sold in the form of sticks
about 8 in (20 cm) long and about 1.25 in (3.2 cm)
in diameter, with a weight of about 0.5 lb (0.23 kg).
Other sizes also exist.
• Dynamite is a high explosive, which means it
detonates rather than deflagrates. While
trinitrotoluene (TNT) is used as the standard for
gauging explosive power, dynamite has more than
a 60% greater energy density than TNT.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-10
Explosions
• This group comprises the majority of
commercial and military blasting, such as
dynamite, TNT, PETN, and RDX.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-11
High Explosives
• In recent years, nitroglycerin-based dynamite
has all but disappeared from the industrial
explosive market and has been replaced by
ammonium nitrate–based explosives (i.e., water
gels, emulsions, and ANFO explosives).
• Secondary explosives must be detonated by a
primary explosive.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-12
High Explosives
• In many countries outside the United States,
the accessibility of military high explosives to
terrorist organizations makes them very
common constituents of homemade bombs.
• RDX is the most popular and powerful of the
military explosives, often encountered in the
form of pliable plastic known as C-4.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-13
High Explosives
• Triacetone triperoxide (TATP) is a homemade
explosive that has been used by terrorist
organizations.
• TATP can be made by combining acetone and
peroxide in the presence of an acid.
• Its existence has led to the banning of most
liquids on commercial aircraft.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-14
Collection and Analysis
• The entire bomb site must be systematically
searched with great care given to recovering any
trace of a detonating mechanism or any other
item foreign to the explosion site.
• Objects located at or near the origin of the
explosion must be collected for laboratory
examination.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-15
Collection and Analysis
• Often a crater is located at the origin and loose
soil and other debris must be preserved from
its interior for laboratory analysis.
• One approach for screening objects for the
presence of explosive residues in the field or
laboratory is the ion mobility spectrometer
(IMS).
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-16
Collection and Analysis
• Preliminary identification of an explosive
residue using the IMS can be made by noting
the time it takes the explosive to move through
a tube. A confirmatory test must follow.
• All materials collected for the examination by
the laboratory must be placed in sealed airtight containers and labeled with all pertinent
information.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-17
Back at the Lab
• Typically, in the laboratory, debris collected at
explosion scenes will be examined
microscopically for unconsumed explosive
particles.
• Recovered debris may also be thoroughly
rinsed with organic solvents and analyzed by
testing procedures that include color spot tests,
thin-layer chromatography, infrared
spectrometry and gas chromatography–mass
spectrometry.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-18
Back at the Lab
• Confirmatory
identification
tests may be
performed on
unexploded
materials by
either infrared
spectrophotometr
y or X-ray
3
diffraction.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
1
2
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-19
X-ray Diffraction
• X-ray diffraction is applied to the study
of solid, crystalline materials.
• As the X-rays penetrate the crystal, a
portion of the beam is reflected by each
of the atomic planes.
• As the reflected beams leave the crystal’s
planes, they combine with one another to
form a series of light and dark bands
known as a diffraction pattern.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-20
X-ray Diffraction
• Every compound is known to produce its own
unique diffraction pattern, thus giving analysts
a means for “fingerprinting” crystalline
compounds.
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-21
X-Ray Diffraction Results
•
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-22
Modern Bombs
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-23
Famous Bomb Sites
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-24
Famous Bombings
• Oklahoma City Bombing 1995 , 168 dead
• Twin World Trade Center 1993 & 2001 ,
3000 dead after 9-11.
• US Embassy barracks 1983
• USS Cole while in port October 2000
• Pan Am Flight Lockerbie, Scotland:
N.Y.-bound Pan-Am Boeing 747 exploded in flight from a
terrorist bomb and crashed into Scottish village, killing all 259
aboard and 11 on the ground
Listing of bombings web site
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-25
Nuclear Bombs
• Normal chemical explosions are different from
nuclear bombs in that they only use the electron
bonds for energy.
• Nuclear bombs use the atomic binding force from
the center of the atom. There are two types of
nuclear bombs: Fission and Fusion. Reference
web site Fission bombs split the nucleus.
• Fusion bombs combine nuclei into larger atoms.
• Nuclear bombs are thousands of times more
powerful than chemical bombs. The biggest
nuclear bomb ever made was equal to 50 million
tons of TNT. Web site video
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-26
History of Nuclear Bombs
Video
• The atomic bomb was first developed by
German and American scientists
including Einstein. The first two fission
bombs were used by the USA on Japan to
end WWII. These are the only 2 ever
used during war on an enemy.
• Over 2000 have been exploded in testing
• The damage from nuclear bombs would
be much greater than chemical bombs.
Video
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-27
Fission Nuclear Bombs
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
Video
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-28
Fusion Nuclear Bomb
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
Video
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-29
Fusion Nuclear Bombs
FORENSIC SCIENCE: An Introduction, 2nd ed.
By Richard Saferstein
How to survive
Video
©2011, 2008 Pearson Education, Inc.
Upper Saddle River, NJ 07458
14-30