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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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Analysis of explosives

Analysis of Explosives


Introduction

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

Chemistry of Explosion

  • Essentially a combustion reaction - like a fire

  • Major difference is speed of reaction

  • Damage caused by rapidly escaping gases and confinement


Types of explosives

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


Types of explosives1

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


Types of explosives2

Types of Explosives

  • Ammonium nitrate based

    • Water gels

    • Emulsions

    • ANFO’s


Analysis of explosives1

Analysis of Explosives

  • Microscopy

  • Thin layer chromatography

    • Visualise with Greiss reagents

  • Infrared spectrophotometry

  • Detonator fragments


The role of forensic science in the investigation of major acts of terrorism

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


Introduction1

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


The world trade center bombing

The World Trade Center Bombing


The scenario

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


Goals of investigation

Goals of Investigation

  • Identify victims

  • Identify explosive

  • Recover bomb and timing device

  • Determine method of delivery


Evidence sought

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


Areas of forensic science

Areas of Forensic Science

  • Explosives

  • Engineering

  • Questioned documents

  • Fingerprints

  • Pathology

  • DNA


World trade center bombing

World Trade Center Bombing


The murrah building oklahoma city

The Murrah Building, Oklahoma City


The scenario1

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


Goals of investigation1

Goals of Investigation

  • Identify victims

  • Identify explosive

  • Find timer and bomb parts

  • Determine method of delivery


Evidence sought1

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


Areas of forensic science1

Areas of Forensic Science

  • Anthropology

  • DNA and serology

  • Pathology

  • Entomology

  • Explosives

  • Trace evidence

  • Engineering

  • Questioned documents

  • Fingerprints


Wtc destruction

WTC Destruction


The scenario2

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


Goals of investigation2

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.


Evidence sought2

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


Areas of forensic science2

Areas of Forensic Science

  • Anthropology

  • DNA and serology

  • Odontology

  • Pathology

  • Entomology

  • Trace evidence

  • Questioned documents

  • Fingerprints

  • Tools and toolmarks


Analysis of explosives

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


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