Forensics Explosions

Explosives An explosion is the product of combustion accompanied by the creation of gases and heat at a rapid rate. As these gases are release from confinement, they produce a blast effect, or an outward rush of gas—at a rate of up to 7,000 mph. These are powerful enough to overthrow walls and collapse roofs.

Explosives An explosive device is comprised of three components: A type of fuel An oxidizer An igniter

Explosives There are two kinds of explosives: Low Explosives— are explosives with a velocity of detonation less than 1,000 meters per second High Explosives— are explosives with a velocity of detonation greater than 1,000 meters per second.

Low Explosives Have a slow burn rate Produce a propelling or throwing action, making them suitable as propellants for ammunition or sky rockets Include black powder and smokeless powder

High Explosives Include: Dynamite TNT PETN RDX Can detonate almost instantaneously at rates of 1,000 to 8,500 meters per second Produce a shattering or smashing effect Usually require a primer and blasting cap Include: Dynamite TNT PETN RDX

High Explosives Classified into two groups: Primary Explosives --easily detonated by heat and shock Secondary Explosives --relatively insensitive to heat and shock and normally needs to be detonated by a primary explosive

Explosives Primary Explosives These explosives are ultrasensitive to heat, shock, or friction and under normal conditions will detonate violently instead of burning. They are used to detonate other explosives through a chain reaction and referred to as primers These explosives provide the major ingredient of the blasting cap

Explosives Secondary Explosives These explosives are relatively insensitive to heat, shock or friction Will normally burn rather than detonate Used in majority of commercial and military blastings

Explosives An x-ray machine can reveal concealed bombs in luggage or mail packages Pipe bomb Grenade

Explosives Trained dogs are able to detect the scent of explosives, even a few yards away. They are useful anywhere--airplanes, schools, hotels, parking lots, etc.

Explosives A bomb scene investigator needs to be able to recognize and collect appropriate samples of un-detonated residue from the site. A high explosive or a contained low explosive creates a crater at the origin of the blast.

Collection of Residue All loose soil and other debris must be removed immediately from the interior of the hole and preserved for laboratory analysis Materials blown away from the blast may too retain explosive residues. All personnel searching the site must wear disposable gloves, shoe covers and overalls Materials are best preserved, separated and sealed in metal containers.

Explosives Bomb scene investigators use: Wire mesh screens to sift through the debris The Ion Mobility Spectrometer (IMS) is a portable detection machine that uses a vacuum to collect explosive residues The Color Spot test for identification of common explosives An Infrared Spectrophotometer to produce a unique “fingerprint” for identification

Explosives Ion Mobility Spectrometer The vaporized residue is converted to electrically charged ions that move through an electric field. Different ions move at different rates depending on their size and structure, which allows for identification.

Bomb Threats Once a bomb threat or a suspicious package has been detected, the bomb squad or a robot can be dispatched to disarm it.

Explosives Tele-operators can navigate a robot from a safe distance to search and remove a bomb.

Olympic Park Bombing On July 27, 1996, a back- pack was left under a park bench near Centennial Olympic Park. Around 1:30am the back- pack exploded, sending nails and shrapnel over 100 yards into the air.

Olympic Park Bombing Though there were many people in attendance during the explosion, only two were killed, Alice Hawthorne and Melih Uzunyol. Over 100 were injured.

Olympic Park Bombing After a lengthy investigation, the FBI searched and apprehended their suspect, Eric Robert Rudolph.

Oklahoma City Bombing On April 19, 1995, Timothy McVeigh detonated a rental truck full of fertilizer and fuel oil which exploded, obliterating half of the nine-story building. This explosion killed 168 men, women and children, and injured 600.