Fs Ch 16

Chapter 16

Forensic Investigation of Explosions

Forensic ScienceRichard Saferstein

© 2009 Pearson Education, Upper Saddle River, NJ 07458.

All Rights Reserved.2

Explosions

Rapid oxidation & production of large quantities of gases

Sudden buildup of gas pressure

High or low explosives:-speed at which explosives decompose




Low Explosives

Most widely used: Black powder:-mixture of potassium or sodium nitrate,

charcoal, and sulfur Smokeless powder:-nitrated cotton (nitrocellulose) or

nitroglycerin and nitrocellulose.




High Explosives Primary explosives:-ultra-sensitive to heat/shock/friction-major ingredients blasting caps/primers

Secondary explosives:-insensitive to heat/shock/friction-burn vs. detonate-small quantities/open air-commercial/military -dynamite/TNT/PETN/RDX




High Explosives Dynamite (nitroglycerine based) -replaced by ammonium nitrate–based

Secondary explosives detonated by primary explosive

Outside US:-terrorist organizations-homemade bombs RDX:-popular/powerful -pliable plastic (C-4)




High Explosives

Triacetone triperoxide (TATP):-homemade explosive-acetone/peroxide/acid-liquids banned on commercial aircraft




Collection and Analysis Entire bomb site:-systematically searched-trace of a detonating mechanism/foreign

item Crater: -origin-loose soil/debris preserved from interior

ion mobility spectrometer (IMS)-preliminary ID is made-requires confirmation




Examining the crater




Car bomb crater




Collection and Analysis Air-tight containers/labeled

Debris/articles from different areas packaged separately

Explosives diffuse through plastic/contaminate




Back at the Lab Microscopically:-unconsumed explosive particles

Rinsed with organic solvents:-color spot tests/GC/MS

Confirmatory identification tests:

Infrared spectrophotometryX-ray diffraction-“fingerprinting” crystalline compounds




X-ray Diffraction

X-ray diffraction:-solid, crystalline materials-penetrate crystal-portion of the beam reflected by atomic planes-leave planes combine to form light and dark

bands-diffraction pattern-each compound unique diffraction pattern-“fingerprinting” crystalline compounds




Taggants Proposed international program:-tiny color-coded chips-sand grains-added at manufacture-recovered at scene-fluorescent/magnetic sensitive




“Signature”

Practice makes perfect:

-MO

-style

-refine w/practice













































































































Technology

Fs Ch 16