Chapter 14 Forensic Investigation of Explostions

Question 1

What produces the violent physical disruption associated with an explosion?

Answer 1

Sudden buildup of expanding gas pressure at the origin of the explosion

Question 2

What is the difference between deflagration and detonation?

Answer 2

Deflagration is characterized by very rapid oxidation that produces heat, light, and a subsonic pressure wave. Detonation is characterized by extremely rapid oxidation that produces a super-sonic shock wave.

Question 3

What is the difference between low explosives and high explosives?

Answer 3

Low explosives detonate relatively slowly (less than 1,000 meters per second), while high explosives detonate very rapidly (from 1,000 to 8,500 meters per second).

Question 4

What is a safety fuse and what is it used for?

Answer 4

A safety fuse consist of black powder wrapped in a fabric or plastic casing. It is used to carry a flame at a uniform rate to an explosive charge.

Question 5

What ingredients are required to create a low explosive?

Answer 5

Fuel and a good oxidizing agent

Question 6

What are the two classes of high explosives? What is the difference between the two classes?

Answer 6

Primary and secondary
Primary explosives are ultrasensitive to heat, shock, or friction, and under normal conditions detonate violently instead of burning. Secondary explosives are relatively insensitive to heat, shock, or friction, and normally burn rather than detonate when ignited in small quantities in open air. Primary explosives usually detonate secondary explosives.

Question 7

What are the main ingredients in straight dynamite? What other substances also are included in modern straight dynamites and what purpose do they serve?

Answer 7

Nitroglycerine and pulp
Modern straight dynamites also include sodium nitrate (which furnishes oxygen for complete combustion) and a small percentage of a stabilizer, such as calcium carbonate

Question 8

What types of explosives largely have replaced dynamite for industrial used? What are the advantages of these types of explosives?

Answer 8

Ammonium nitrate- based explosives largely have replaced dynamite for industrial uses
They are cheap and very stable

Question 9

What is ANFO?

Answer 9

Explosive consisting of ammonium nitrate soaked in fuel oil

Question 10

Which is the most powerful and popular military explosive?

Answer 10

RDX

Question 11

What is a detonator? What is the composition of most detonators?

Answer 11

Device used to create an explosion needed to ignite a high explosive
In most cases, detonators are blasting caps composed of copper or aluminum cases containing lead azide

Question 12

What is the most obvious postexplosion characteristic of a high or contained low explosive?

Answer 12

The presence of a crater at the origin of the blast

Question 13

How are soil and other soft loose materials collected at the scene of an explosion best stored?

Answer 13

Metal containers

Question 14

What is the first procedure typically used to analyze bomb-scene debris that arrives in the laboratory?

Answer 14

When bomb-scene debris and other materials arrive at the laboratory, everything is first examined microscopically to detect particles of unconsumed explosive.

Question 15

List three procedures commonly used as screening tests for explosive residues.

Answer 15

a. Color spot tests
b. Thin-layer chromatography (TLC)
c. Gas chromatography/ mass spectrometry

Question 16

Name two confirmatory tests for the presence of intact explosives located in debris.

Answer 16

a. Infrared spectrophotometry

b. X-ray diffraction

Question 17

What is a taggant? What purpose do taggants serve?

Answer 17

Taggants are tiny color-coded chips the size of sand that are added to commercial explosives during their manufacture. The taggant chip is arranged in a color sequence that indicates where the explosive was made and when it was produces. Taggants thus allow an explosive to be traced through its distribution chain to its final legal possessor.