Module 5: Forensics of Explosives Investigation

Explosion def

sudden, violent release of expanding gases, not always caused by explosives

Explosives def

substances that undergo rapid oxidation reaction with production of large quantities of gases

Speed at which explosives decompose to gas defines classification as….

high or low explosives

Deflagration

Oxidative decomposition or burning where propagation of gas slower than speed of sound

Diffference between delagration and detonation?

deflagration: Slower than speed of sound, Detonation: faster than speed of sound

Common explosives in the low-explosive group are….

black powder and smokeless powder.

Black powder is a mixture of….

potassium or sodium nitrate, charcoal, and sulfur (commonly used in pyrotechnics, propellent in muzzleloading firearms, military primers/igniters)

Smokeless powder consists of….

nitrated cotton (nitrocellulose) or nitroglycerin and nitrocellulose ( used as propellant in modern firearms/artillery for efficiency, energy output, and clean-burning)

Low explosives are often…..

confined to a container like a pipe (e.g., gun barrel).

Low explosives are often confined to a container like a pipe (e.g., gun barrel). The speed of decomposition is called _____

deflagration

Detonation: When speed of reaction front > speed of sound, creating a….

shockwave when pressure wave of gas exceeds speed of sound

Detonation of explosives -….

supersonic, rapid chemical decomposition driven by a powerful shock wave.

Detonation: Converts solid or liquid explosive material into…..

large volume of superheated, high-pressure gases within microseconds, releasing a tremendous amount of energy

High Explosives: Primary explosives….

ultra-sensitive to heat, shock, or friction; provide major ingredients found in blasting caps or primers used to detonate other explosives.

High Explosives: Secondary explosives…..

relatively insensitive to heat, shock, or friction and normally burn rather than detonate if ignited in small quantities in the open air.

Secondary explosives: comprises majority of….

commercial/military blasting, such as dynamite, TNT, PETN, and RDX.

Secondary explosives must be detonated by…

primary explosive

Speed of decomposition is known as….

Detonation

Speed of decomposition is known as detonation. Its extremely rapid producing a….

supersonic shock wave creating a blast effect with an outward rush of gases at speeds as high as 10,000 km/hour.

Nitroglycerin-based dynamite has all but disappeared from industrial explosive market and has been replaced by…

ammonium nitrate-based explosives

In many countries outside the United States, accessibility of military high explosives to terrorist organizations makes them very common…..

constituents of homemade bombs.

RDX

is most popular and powerful of military explosives, often encountered in the form of pliable plastic known as C-4.

Triacetone triperoxide (TATP) is a….

homemade explosive that has been used by terrorist organizations.

TATP can be made by combining…

acetone and peroxide in presence of an acid.

TATP Its existence has led to banning of….

most liquids on commercial aircraft

Entire bomb site must be systematically searched with great care towards recovering….

any trace of a detonating mechanism or any other item foreign to the explosion site

Bomb site: Objects located at or near the origin of the explosion must be…

collected for laboratory examination.

Bomb site: Often a crater is located at origin and….

loose soil and other debris must be preserved from for laboratory analysis.

pressure cooker bombs used in Boston Marathon bombing were IEDs made from….

6-liter pressure cookers packed with low explosive powder, shrapnel (nails and metal ball bearings), and an adhesive

Bomb site: All materials collected for examination by laboratory placed in…

sealed air-tight containers

Bomb site: Materials will have traces of…..

unconsumed explosives that can be identified (X-ray diffraction if crystals)

Bomb site: Debris and articles collected from different areas are packaged in….

separate air-tight, metal containers as some explosives can diffuse through plastic and contaminate nearby containers.

Bomb site: Debris has yielded…

DNA and fingerprints despite damage and heat of explosion

Lab protocols bomb: Typically, debris collected at explosion scenes will be examined…

microscopically for unconsumed explosive particles.

Lab protocols bomb: Recovered debris may also be thoroughly rinsed with….

organic solvents and analyzed by testing procedures that include color spot tests, thin-layer chromatography, and gas chromatography/mass spectrometry

Lab protocols bomb: Confirmatory identification tests may be performed on….

unexploded materials by infrared spectrophotometry