ExplosivesCHS Science Dept.

Forensics

Definitions• Explosion- A chemical or

mechanical action resulting in the rapid expansion of gasses.

• Deflagration- A very rapid oxidation reaction accompanied by a low intensity pressure wave with a disruptive effect.

Definitions cont• Detonation- an extremely

rapid oxidation reaction accompanied by a violent disruptive effect and an intense, supersonic shock wave.

Types of explosives• High Explosive- Explosives

with a velocity of detonation greater than 1000m/s (meters per second).

• Low Explosive- Explosives with a velocity less than 1000m/s.

Low Explosives• Most widely used low-

explosives group are black powder and smokeless powder.

• Gunpowder burns, it is only explosive when confined.

Sulfur, Potassium nitrate, Charcoal Nitrocellulose

Low explosives• Natural gas mixed with air.• Can cause large

explosions

High Explosives

• Primary Explosives- are ultra-sensitive to heat, shock, or friction and will normally detonate rather than burn.

• Due to this characteristic they are used to detonate other explosives and are often called

Primers

High Explosives• Dynamite was discovered by

Alfred Nobel when he mixed diatomaceous earth with nitroglycerine making it less sensitive

High Explosives• Commercial explosives

–ANFO Ammonium Nitrate Fuel Oil

Jig saw activity• Military high explosives page 456

• TATP page 454• Nitrate Ammonium Explosives page 453

Explosives Unit• The Explosives Unit (EU)

conducts examinations of evidence associated with bombing matters.

• The unit conducts forensic examinations of:

• Improvised Explosive Devices (IEDs), Incendiary Devices, and their respective remains

• While providing expert witness testimony in court regarding the results of these examinations.

• The EU also provides direct field support in: –Bombing matters –Bombing crime scene investigations

–Searches of bomb factories and safe houses in which bombs or bomb components may be encountered.

• The EU also performs chemical analyses to determine the type of explosive used in an improvised explosive or incendiary device.

• This includes analyzing bulk substances and the residues left behind after an explosive detonates.

False alarms• Some of the calls to the

bomb squad are false alarms or pranks

Equipment• Bomb containment• Bomb Suit• Search Mirror• Disruptor- shoots high

pressure H2O to disarm bombs

• Detectors• Endoscopes

Robots

Refrences• http://www.fbi.gov/hq/lab/lab2006/

labannual2006.htm#22

References• Saferstein, Richard. Criminalistics an introduction to forensic science. Upper Saddle

River, N.J: Prentice Hall, 2004. Print. •

Pictures• Slide 2

– http:// www.hsvpolice.com/News%20Releases/bomb_squad_vehicle.jpg• Slide 3

– http://www.insidesocal.com/sgvcrime/MOLOTOV.jpg– http://www.globalsecurity.org/military/intro/images/ied-cutout01.jpg

• Slide 6– http://www.thebostonchannel.com/2007/0131/10891659_400X300.jpg

• Slide 8– http://miamiherald.typepad.com/crime_scene/2009/02/page/2/– http://www.made-in-china.com/image/2f0j00vMATmJaBSUgwM/EOD-

Bomb-Disposal-Suit-BD2010-.jpg– http://www.fieldforensics.com/blast-containment.htm– http://www.made-in-china.com/image/2f0j00MByaIJWhbRurM/Disruptor-

AL-LNDK-.jpg– http://www.bulletproofbodyarmorhq.com/catalog/images/eod20.jpg

• Slide 9– http://www.armedforces-int.com/images/companies/958/bomb-disposal-

robots-3b.jpg

Pictures• Slide 2

– http://www.hnd.usace.army.mil/pao/CEAInfo/Explosion%20Photo.JPG

• Slide 5– http://upload.wikimedia.org/wikipedia/commons/d/df/

Pyrodex_powder_ffg.jpg– http://www.aiexplosives.com/Files/Image/Smokeless

%20powder.jpg• Slide 6

– http://www.treehugger.com/landfill-gas-flare.jpg– http://media.sacbee.com/smedia/2008/12/24/17/835-

explos10.standalone.prod_affiliate.4.jpg• Slide 7

– http://upload.wikimedia.org/wikipedia/commons/4/40/Nitroglycerin-2D-skeletal.png

• Slide 8– http://blogs.sfweekly.com/thesnitch/

Nobel_medal_dsc06171.jpg– http://www.urbanrivers.org/drawingdiatoms/diatom.jpg