FORENSIC INVESTIGATION OF EXPLOSIONS Chapter 13
Explosions Definition: Explosives are substances that undergo a rapid oxidation reaction with the production of large quantities of gases. • The sudden buildup of gas pressure produces the explosion. • The speed in which explosives decompose classifies them as either low or high explosives. EXPLOSIONS
Low Explosive • Most commonly used low-explosive: black powder smokeless powder • Black powder - a mixture of potassium or sodium nitrate, charcoal, and sulfur. • Smokeless powder - nitrated cotton (nitrocellulose) or nitroglycerin and nitrocellulose.
Other Explosives High explosives Primary are ultra-sensitive to heat, shock, or friction and provide the major ingredients found in blasting caps or primers used to detonate other explosives. • Secondary explosives (commercial, military, RDX) are insensitive to heat, shock, or friction and burn rather than detonate if ignited in small quantities in the open air. EXPLOSIONS
High Explosives • Nitroglycerin-based dynamite has been replaced in the industrial explosive market by ammonium nitrate–based explosives (i.e., water gels, emulsions, and ANFO explosives). • Secondary explosives must be detonated by a primary explosive. • Accessibility of military high explosives outside the U.S. to terrorist organizations to make homemade bombs. • RDX is the most powerful military explosives, aka plastic C-4. EXPLOSIONS
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. EXPLOSIONS
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. • 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). EXPLOSIONS
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. • Debris and articles collected from different areas are to be packaged in separate air-tight containers. • It has been demonstrated that some explosives can diffuse through plastic and contaminate nearby containers. EXPLOSIONS
Back at the Lab Debris collected at explosion scenes are inspected with a microscope for unconsumed explosive particles. • Recovered debris may be rinsed with organic solvents • color spot tests, thin-layer chromatography gas chromatography–mass spectrometry. • Identification of unexploded materials IR-spectrophotometry or X-ray diffraction. EXPLOSIONS
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. • Every compound is known to produce its own unique diffraction pattern, thus giving analysts a means for “fingerprinting” crystalline compounds. EXPLOSIONS
Home-grown Terrorism http://video.google.com/videoplay?docid=-2449575330029419184# KWTV- Oklahoma City Bombing http://www.youtube.com/watch?v=m6qMXpoE8Hs
Military suspends outdoor weapons testing at Picatinny Arsenal • by Jonathan Casiano/The Star-Ledger Saturday April 12, 2008, 2:55 PM A day after an errant artillery fragment crashed through the roof of a Jefferson Township home, the Army announced today that it was suspending outdoor weapons testing at Picatinny Arsenal until further notice. In this case, Army personnel were using explosive charges to detonate a 15-pound Comp B explosive.as part of a research and development exercise, Picatinny spokesman Peter Rowland said. The exercise was conducted 8 times on Friday, April 11, 2008. Scientific estimates had indicated that fragments from the explosion would travel no further than 400 meters. However, the fragment that landed inside the Angle home traveled some 1,800 meters. Between 2 and 3 p.m. Friday, a two pound hunk of artillery crashed through the roof of Cheryl Angle's home on Longwood Lake Road in the Oak Ridge section of Jefferson Township. The hot metal landed on her 10-year-old daughter's bed and injured the family cat. The cat was later euthanized because of its injuries. Angle's daughter, Cassandra, was not home at the time. Ironically, the Army says the accident occurred while it was testing safer way to dispose of unwanted artillery shells.
Follow-up 2012 • NJ family sues over shrapnel that killed its cat • April 27, 2012, 4:29 p.m. • JEFFERSON TOWNSHIP, N.J. (AP) — A northern New Jersey family is suing the U.S. Army over an errant projectile from Picatinny Arsenal that crashed through their roof in 2008 and killed their cat. • Frederick and Cheryl Angle filed the lawsuit Friday after rejecting a settlement offer of $7,400.