Forensic Science Unit 8, Module 8 Study Guide
Low Explosives
decompose slowly and include black powder and smokeless powder
natural gas explosions
-A sizable amount of natural gas needs to mix with air before the low explosive is created, but if this mixture is ignited, it will produce a large amount of heat and gas
analyzing explosive evidence in the lab
-Black and smokeless powder residue are both fairly easy to recognize to a trained eye because of their distinctive shapes under the microscope -However, most high explosive residues are difficult to pick out under a microscope and other methods are often used to detect these materials -For example, acetone may be rinsed over materials to wash off the explosive residue -This can then be analyzed by x-ray defraction or other techniques
bomb investigators
-Bomb investigation is typically undertaken by highly specialized forensic scientists *These individuals are often trained not only to analyze a bombed crime scene, but also with bomb disposal and the criminal investigation related to explosions *They need to be able to identify the chemical residues at a crime scene that indicate that a bombing took place, as well as the materials used in that bomb -They also work to identify how the bomb was set off
color chips
-One advance in explosives that has been proposed is the use of small color chips -These chips would be added to explosive materials available to the public -Some of these chips would be expected to survive the explosion -The chips would be color coded to help identify what the explosive material is, where it was produced, and when it was produced -This would allow forensic scientists and crime investigators to track down the distribution pattern of the explosive and possibly, who bought it -Currently, only a few countries, including Switzerland, are thinking of adopting this technology
storage of explosive evidence
-Softer materials like insulation and wood are particularly useful as they may retain evidence better than harder materials -an ion mobility spectrometer (IMS), which uses a vacuum to test for explosive materials -Any materials or evidence collected are put into airtight containers
Substrate controls
-an uncontaminated sample
Accelerants
-any substance used to start a fire
Molotov Cocktails
-bombs made by placing gasoline in a glass jar and using an ignitive source
Low explosives
-decompose slowly and include black powder and smokeless powder
primary explosives
-easily ignited or detonated and are very sensitive to heat and friction
political bombing vs. bombings by individuals
-more advanced than individual bombings -most individual bombings are made homemade
Search warrants at fire station
-not needed
Explosion
-occurs when gases expand because of a chemical or mechanical action
Point of Origin
-place where the fire began
"Sniffer"
-takes in air from around a suspected point or material
Speed of blast effect
-the outward rush of gases from the bomb's site of origin can be as high as 7,000 miles per hour
High explosives
-these materials ignite almosy instantaneously and include dynamite and TNT
secondary explosives
-usually much less sensitive to heat and friction and they typically have to be ignited through the use of other explosive materials
Ion Mobility Spectrometer
A vacuum to test explosive materials
Accelerant
Any substance used to start a fire
Molotov Cocktail
Bombs made by placing gasoline in a glass jar and using an ignition source
Hydrocarbons
Compounds that consist of Hydrogen and Carbon
Primary Explosives
Easily ignited or detonated and very sensitive to heat and friction
Point of Origin
Place where a fire began
Blast Effect
The outward rush of gases from the bomb's site or origin
High Explosives
These materials ignite almost instantly and include dynamite and TNT
Substrate Control
Uncontaminated sample
Secondary Explosives
Usually much less sensitive to heat and friction and they typically have to be ignited through the use of other explosive materials
Explosions
When gases expand because of a chemical or mechanical explosion