Explosives 1m2q4a

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

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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

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Explosions A chemical explosive is a compound or a  mixture of compounds which, when  subjected to heat, impact, friction, or shock,  undergoes very rapid, self­propagating,  heat­ producing decomposition.

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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Explosions

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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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

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Gunpowder • The most widely used explosives in the low­ explosive 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

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Explosions • Among the high explosives, primary explosives  are ultra­sensitive 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

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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

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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

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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. 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

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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

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High Explosives • In recent years, nitroglycerin­based 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

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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 C­4.

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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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

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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

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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

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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 air­ tight 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

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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,  thin­layer 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

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Back at the Lab • Confirmatory  identification  tests may be  performed on  unexploded  materials by  either infrared  spectrophotometr y or X­ray  3 diffraction.

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

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©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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X­ray Diffraction • X­ray diffraction is applied to the study  of solid, crystalline materials.  • As the X­rays 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

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X­ray 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

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X­Ray Diffraction Results •  

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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Modern Bombs

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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Famous Bomb Sites

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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Famous Bombings  • Oklahoma City Bombing 1995  ,  168 dead • Twin World Trade Center 1993 & 2001 ,  3000 dead after 9­11. • 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

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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

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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

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Fission Nuclear Bombs

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

Video

©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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Fusion Nuclear Bomb

FORENSIC SCIENCE: An Introduction, 2nd ed. By Richard Saferstein

Video

©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458

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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

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