Analysis of Explosives Ms. Scribner’s Forensic Science Class—Eisenhower High School

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

Explosives Combustion (or decomposition) of explosives occurs so rapidly, that there isn’t enough time for the oxygen in the surrounding atmosphere to combine with the fuel. Therefore, many explosives must have their own source of oxygen – or oxidizing agents

Definitions Explosion—sudden release of chemical or mechanical energy caused by an oxidation or decomposition reaction that produces heat and a rapid expansion of gases.

Definitions Reagent—a substance used to produce a chemical reaction to detect, measure, or produce other substances. Spot tests can be administered to identify

IED--An improvised explosive device is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery round, attached to a detonating mechanism. IEDs are commonly used as roadside bombs.

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

Definitions High explosives—chemicals that oxidize extremely rapidly, producing heat, light and a shock wave; will explode even if not confined Low explosives—chemicals that oxidize rapidly, producing heat, light, and a pressure wave; will explode only when confined.

Types of Explosives Low explosives Escaping gases up to about 3000fps (foot per second) 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 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

Classification by Use Commerical Explosions: Ammonium Nitrate fuel oil (ANFO), black powder, dynamite Military Explosions: RDX (commonly known as C-4), PETN, PETN mixed with TNT to make grenades IED—low explosives placed into confinded containers

Ammonium nitrate based Water gels Emulsions-- are intimate mixtures of oxidizers and carbonaceous fuels made as water in oil type of Emulsions used for blasting in quarries, stripping in underground metal mines, tunneling, well sinking, and road construction. ANFO’s-- ammonium nitrate/fuel oil) is a widely used bulk industrial explosive mixture

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

Microscopic Examination Perforated disc Tube Ball Disc Rod Lamel

1, 2, and 3 step Explosive Trains Explosive Trains

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

A forensic science technician, also referred to as a criminalist, gathers, interprets and analyzes evidence using forensic science techniques and tests. Analyze and test tissue samples Test chemical substances and physical materials Interpret lab findings Collect criminal evidence Reconstruct crime scenes Testify as expert witness during trials

First World Trade Center Bombing

1993 The Scenario—first bombing attempt Urea nitrate bomb put into truck and driven into underground WTC garage and parked at 4 th 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 Identify victims Identify explosive Recover bomb and timing device Determine method of delivery

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 Explosives Engineering Questioned documents Fingerprints Pathology DNA

The Murrah Building, Oklahoma City Domestic Terrorism

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 Investigation Identify victims Identify explosive Find timer and bomb parts Determine method of delivery

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 Science Anthropology DNA and serology Pathology Entomology Explosives Trace evidence Engineering Questioned documents Fingerprints

WTC Destruction-2001

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 4min video

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 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 Science Anthropology DNA and serology Odontology Pathology Entomology Trace evidence Questioned documents Fingerprints Tools and toolmarks

Boston Bombing—April 15, 2013

Two pressure cooker bombs exploded during the Boston Marathon at 2:49 pm killing 3 people and injuring an estimated 264 others. The bombs exploded about 12 seconds and 210 yards (190 m) apart, near the finish line on Boylston Street

A pressure cooker bomb is an The IED was created by inserting explosive material into a pressure cooker and attaching a blasting cap into the cover of the cooker. Pressure cooker bombs have been used in a number of attacks Mumbai train bombings, 2010 Stockholm bombing (failed to explode), 2010 Times Spare car bombing attempt (failed to explode)

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 the object was left at the scene.

Evidence Sought Photos of person of interest Personal effects Bomb parts; timer, casing, etc. Explosive residue Constraining devices such as pieces of the pressure cooker, wire or duct tape

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