14-1 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein FORENSIC INVESTIGATION OF EXPLOSIONS Chapter 14

14-2 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein 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. Antares Rocket Explosion

14-3 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Explosions An explosion is the product of combustion by the creation of gases and heat. How is this different from fire? VERY RAPID reaction

14-4 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Explosions Oxidation reactions for fire use available air as the sole source of oxygen Many explosives need their own source of oxygen because the reaction is so rapid. Chemicals that supply oxygen are known as oxidizing agents

14-5 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Shock Wave Explosives are substances that undergo a rapid exothermic oxidation reaction, producing large quantities of gases. This sudden buildup of gas pressure constitutes the nature of an explosion.

14-6 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Shock Wave The gaseous products of an explosion suddenly expand and compress layers of surrounding air as they move outward from the origin – and if they travel faster than the speed of sound, a shock wave is also created.

14-7 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Explosives The speed at which explosives decompose permits their classification as Low explosives High explosives

14-8 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Explosives Low explosives Fuel + oxidizing agent + container Burn rate is less than 1000 meter/second Deflagration – produces heat, light and a subsonic pressure wave Most widely used are black powder and smokeless powder

14-9 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Low Explosives Black powder is a mixture of potassium nitrate or sodium nitrate, charcoal, and sulfur. VideoVideo Smokeless powder consists of nitrated cotton (nitrocellulose) or nitroglycerin and nitrocellulose. VideoVideo Chlorates plus sugar in a small container Natural gas and air in a confined space

14-10 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Types of Explosives High explosives Include dynamite, TNT, PETN and RDX Burn rates are 1000 –8,500 meters/second Does not require a container Detonation produces a supersonic shock with within the explosive charge –Primary Explosives –Secondary Explosives Rocket Fuel Explosion

14-11 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein High Explosives Primary explosives Ultra-sensitive to heat, shock, or friction Detonate violently instead of burning Major ingredients found in blasting caps or primers used to detonate other explosives. Rarely used as the main charge in a homemade bomb. Blasting Caps

14-12 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein High Explosives Secondary explosives Relatively insensitive to heat, shock, or friction Normally burn rather than detonate if ignited in small quantities in the open air Majority of commercial and military blasting, –dynamite, TNT, PETN, RDX and tetryl Secondary explosives must be detonated by a primary explosive –Blasting caps can be initiated by burning a safety fuse or an electrical current

14-13 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Secondary Explosives Dynamite Invented by the Swedish chemist Alfred Nobel Dynamite is usually sold in the form of sticks about 8 in long weighing about 0.5 lb. a. Sawdust soaked in nitroglycerin. b. Protective coating surrounding the explosive material. c. Blasting cap. d. Electrical cable (or fuse) connected to the blasting cap.

14-14 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Secondary 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).

14-15 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Secondary Explosives Water Gels Consistency of gelatin or gel-type toothpaste Water resistant –Blasting under wet conditions

14-16 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Secondary Explosives Emulsion explosives Consist of two distinct phases – an oil phase and a water phase Usually contain micron-sized glass, resin or ceramic spheres – microspheres –Size of the sphere controls the explosive’s sensitivity and detonation velocity

14-17 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Secondary Explosives ANFO explosives Ammonium nitrate soaked in fuel oil Used in blasting operations in the mining industry Fertilizer is an easy to obtain form of ammonium nitrate for homemade bombs

14-18 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Secondary Explosives TATP (triacetone triperoxide) Homemade explosive used by terrorist organizations. Combines acetone, peroxide and an acid. Reason most liquids are banned on commercial aircraft.

14-19 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Secondary Explosives Military High Explosives RDX is the most popular and powerful military explosive Most common form is a form of pliable plastic known as C-4 WWII – TNT used as bursting charge explosive –Bombs, shells, grenades PETN used in small-caliber projectiles –Detonating cord or primacord

14-20 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection of Evidence Most important step is to collect appropriate samples from the explosion scene. Bomb-scene investigator’s skill and ability to recognize and sample areas most likely to contain these materials

14-21 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein 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.

14-22 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection of Evidence Often a crater is located at the origin and loose soil and other debris must be preserved from its interior for laboratory analysis.

14-23 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection of Evidence Also look for objects near the origin of the detonation Wood, insulation, rubber and other soft materials often collect traces of the explosive Materials blown away from origin may also have explosive residue

14-24 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Analysis One approach for screening objects for the presence of explosive residues in the field or laboratory is the ion mobility spectrometer (IMS).

14-25 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Analysis A sample is collected with a vacuum or wiped down with Teflon-coated fiberglass disc.

14-26 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Analysis Explosive residue is vaporized by heat and then exposed to radioactive nickel which converts the sample into ions

14-27 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Analysis Ions move through the drift region and separate based on their speed as the move through an electric field

14-28 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein 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. The IMS can detect plastic explosives as well as commercial and military explosives.

14-29 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Collection and Packaging All materials collected for the examination by the laboratory must be placed in sealed air-tight containers and labeled with all pertinent information. Evidence from each area must be packaged in different containers Plastic bags ARE NOT used

14-30 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Back at the Lab First, debris is examined microscopically for unconsumed explosive particles. Possible detonators are also examined microscopically for residue –Black powder and smokeless powder are relatively easy to locate because of their characteristic shape and color

14-31 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Back at the Lab After microscopic examination, evidence is rinsed with a solvent to dissolve other explosive residues. Most high explosives dissolve in acetone Water gel, ammonium nitrate-based explosives or suspected low explosives should be rinsed with water so that nitrates and chlorates can be extracted.

14-32 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Back at the Lab Acetone and water extracts are screened by testing procedures that may include color spot tests thin-layer chromatography infrared spectrometry gas chromatography–mass spectrometry

14-33 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Back at the Lab With sufficient amounts of recoverable explosives, confirmatory identification tests may be performed using either infrared spectrophotometry or X-ray diffraction

14-34 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein X-ray Diffraction Every compound is known to produce its own unique diffraction pattern, thus giving analysts a means for “fingerprinting” crystalline compounds.

14-35 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Proposed Taggant Program Tiny color-coded chips the size of sand grains are added to commercial explosives during their manufacture Some of the chips survive explosion and can be traced back to when and where it was produced.

14-36 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Nuclear Bombs Normal chemical explosions use the electron bonds for energy. Nuclear bombs use the atomic binding force from the center of the atom. Two types of nuclear bombs Fission Bombs –split the nucleus Fusion bombs –combine nuclei into larger atoms

14-37 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Fission Nuclear Bombs Video

14-38 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Fusion Nuclear Bomb Video

14-39 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein History of Nuclear Bombs 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

14-40 ©2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein Nuclear Bombs 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. The damage from nuclear bombs would be much greater than chemical bombs. VideoVideo