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Analysis of Explosives

Analysis of Explosives. Introduction. Most bombing incidents involve homemade explosive devices There are a great many types of explosives and explosive devices Lab must determine type of explosives and, if possible, reconstruct the explosive device. Chemistry of Explosion.

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Analysis of Explosives

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  1. Analysis of Explosives

  2. Introduction • Most bombing incidents involve homemade explosive devices • There are a great many types of explosives and explosive devices • Lab must determine type of explosives and, if possible, reconstruct the explosive device

  3. Chemistry of Explosion • Essentially a combustion reaction - like a fire • Major difference is speed of reaction • Damage caused by rapidly escaping gases and confinement

  4. Types of Explosives • Low explosives • Escaping gases up to about 3000fps • Crucial element is physical mixture of oxygen and fuel • Examples are black and smokeless powders • Black powder is mixture of potassium nitrate, charcoal and sulfur • Smokeless powder is nitrocellulose and perhaps nitroglycerine

  5. Types of Explosives • High explosives • Velocity of escaping gases up to 10,000fps • Oxygen usually contained infuel molecule • Two types • Initiating - Senistive, will detonate readily when subjected to heat or shock. Used to detonate other explosives in explosive train • Noninitiating - relatively insensitive, requires heat or shock. Includes TNT or PETN

  6. Types of Explosives • Ammonium nitrate based • Water gels • Emulsions • ANFO’s

  7. Analysis of Explosives • Microscopy • Thin layer chromatography • Visualise with Greiss reagents • Infrared spectrophotometry • Detonator fragments

  8. The Role of Forensic Science in the Investigation of Major Acts of Terrorism

  9. Introduction • A major terrorist act can generate huge amounts of evidence that can help in the investigation • Different acts call for different strategies • This talk will examine three major terrorist acts in the US during the past 10 years with emphasis on the forensic science aspects: • World Trade Center Bombing • Murrah building in Oklahoma City bombing • World Trade Center destruction

  10. The World Trade Center Bombing

  11. The Scenario • Urea nitrate bomb put into truck and driven into underground WTC garage and parked at 4th level down • Subsequent explosion did extensive damage to several levels of the garage and less damage to other levels • Although goal was to topple WTC, little structural damage was done • Some loss of life

  12. Goals of Investigation • Identify victims • Identify explosive • Recover bomb and timing device • Determine method of delivery

  13. Evidence Sought • Investigators had to remove large quantities of concrete, steel and cars to get to bomb seat • Bomb seat contained most of the important evidence • Bomb parts; timer, casing, etc. • Explosive residue • Parts of truck that contained explosive

  14. Areas of Forensic Science • Explosives • Engineering • Questioned documents • Fingerprints • Pathology • DNA

  15. World Trade Center Bombing

  16. The Murrah Building, Oklahoma City

  17. The Scenario • ANFO explosive and timer packed into a rented truck, which was then parked outside Murrah building • Explosive confined to closed space such as truck is much more powerful • Resulting explosion resulted in severe damage to building and loss of more than 100 lives

  18. Goals of Investigation • Identify victims • Identify explosive • Find timer and bomb parts • Determine method of delivery

  19. Evidence Sought • Easier to find than in WTC because bomb seat outside building • Explosive residues • Bomb parts • Bodies and body parts; cadaver dogs, flies • Personal effects; helps in identification of human remains

  20. Areas of Forensic Science • Anthropology • DNA and serology • Pathology • Entomology • Explosives • Trace evidence • Engineering • Questioned documents • Fingerprints

  21. WTC Destruction

  22. The Scenario • Large airplanes, loaded with fuel, crash into WTC buildings • Raging fires ignite everything in building above crash sites. • Metal supports melt from heat • Building collapses due to inability to support its own weight after structural damage • Thousands of people killed

  23. Goals of Investigation • Cause known, no need to determine how destruction occurred • Recover and identify bodies, parts of bodies and charred remains • Recover personal effects that might help identify victims or perpetrators • Evidence that might determine how hijackings occurred.

  24. Evidence Sought • Bodies and body parts; cadaver dogs, flies • Charred remains • Personal effects • Trace evidence such as charred papers • Weapons such as knives • Constraining devices such as wire

  25. Areas of Forensic Science • Anthropology • DNA and serology • Odontology • Pathology • Entomology • Trace evidence • Questioned documents • Fingerprints • Tools and toolmarks

  26. http://www.youtube.com/watch?v=3-jeQmW5wiA&feature=related

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