jimtrue.com : school : CJT2141 : 11: Arson & Explosives
Posted by Jim True on March 19, 2003 6:00 AM. Last Updated October 22, 2006 9:23 PM
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ARSON
Oxidation - whenever an item reacts with oxygen
Examples:
-Rust is Iron reacting with Oxygen)
-Alcohol breaks down with Oxygen, it oxidizes in the blood)
Oxygen is mixing with a fuel to give off Carbon Dioxide, Heat and Water
Fire Triangle (Fuel, Oxygen & Heat) - If you can remove one of these elements the fire will extinguish.
Fire as it occurs is an Oxidation reaction.
Adding Energy is what causes the fast reaction of a Fire (slow reaction is rust in Oxidation).
Endothermic - Requires Energy to be put into it to make it go
Exothermic - Releases Energy as reaction occurs (Fire, Explosion)
Sulfuric Acid mixes with Formaldehyde creates heat through an Endothermic Reaction
Need a certain amount of energy to get you over the hump to begin the Endothermic or Exothermic reaction.
Fire gives off energy (once it is started) in the form of heat and light.
1. Flashpoint - Lowest temperature for vapor to be given off to begin the chain reaction to begin the fire.
Vapors are catching fire which fuels the fire (the chain reaction)
(Fuel mixture, vapor must be at the right level)
2. Flammable Range - Vapor concentrations are at their most opportunistic point for a fire to start {ie. Gasoline 1.3 - 6% Flammable Range).
3. Pyrolysis - Burning something up to bring it to a vapor state.
Spontaneous Combustion - (bio-organisms eating decomposing matter, methane gas - linseed oil and bacteria, anaerobic environment).
Glowing Combustion - Coals, Cigarette, tops of electric stoves (you can see the heat and energy but no flame), smoldering. Volcano. Welding.
Have to have the energy to initiate the fire, once over the energy hump, must have the fuel to sustain the fire.
Arson Investigator (EVERY Fire Investigator, Fire Marshall, or Arson Investigator)
1. Where did the fire start?
2. How did it start?
3. Was it accidental or not?
Arson is one of the hardest cases to prosecute. Not only property crimes, often used to cover a homicide or suicide.
Firemen have their job to do (putting out the fire, breaking windows, soaking things, destructive to the crime scene).
Point of Origin - Beginning of the fire
Fire by its nature has a natural movement, up and outwards.
Wall will have a V-Pattern in soot, follow the v-pattern down to the point of origin. Can be multiple points of origin.
Start investigation at the Point of Origin. If leads to Electrical Outlet, could be an electrical outlet.
Was it an electrical fire? Grease Fire on the stove? Kid playing with matches? Cigarettes?
Intentionally Set or Incendiary = Arson
Fire starts at the top where the vapors mix with the oxygen and fire. Start at the point of the origin and look under it to see if accelerant residue exists at the point where the fire starts.
Pyrolysis - of products, petroleum based products throw off the sniffers.
Best tool for determining Arson detection is Arson K-9 (Labrador retrievers) Dogs are imprinted on SPECIFIC accelerants. Does a wonderful job at finding the point of origin. Drafts in outdoor scenes can foil the dog's ability to find the actual origin.
Screening test only, not for confirmation.
Pictures of the whole point of origin.
Dig out the debris at the point of origin, put into an airtight container. Paint Cans, Mason Jars (in Canada, NE areas), KAPAK, Polyetheline bags, heat sealed pouch. Feds and ATF uses KAPAK (heat sealable). Same principle as shrink wrap.
When looking at the debris, fill up the paint can, no more than HALFWAY. Because you hope you have some of the accelerant in the debris. Also collect a Control sample from another area that is NOT the point of origin.
Lab has to find a way to collect the sample:
ATF - Primary Method, mastered by the ATF: Charcoal Strip, Passive Absorption
Heat the paint can to 75 degrees celsius, put a carbon strip on a piece of dental floss and paper clip (like fishing). Vapors will be driven up by the heat, and collect into the carbon strip. 1/2 is left with the can for evidence, the other is used for the sample test.
Strip is soaked in Carbon disulfide, act like a solvent sponge to pull off a sample.
FBI: Pentane Wash, pour the debris into the Pentane and swirl it around, extract the solvent.
Petroleum Distillates - Light (lighter fluid), Medium (Paint thinner, charcoal lighter), heavy (diesel fuel, kerosene)
Headspace Extraction with a Gas Syringe for Light end Petroleum distillates.
Sample is injected into a Gas Chromatograph, and then ran through GC/MS.
FID - Flame Ionization Detector (Carbon Counter, used to use for Accelerant Detection). Petroleum distillates have 150 components or more.
Mass Spectrometer helps to discriminate pyrolysis products.
Other evidence, look for pry marks, look for fingerprints (there will still be areas that are protected or undamaged). Broken glass (was it broken in or broken before the fire started).
A lot of vehicular arsons, too, where did the fire start?
Was that petroleum distillate supposed to be there?
Class evidence - cannot tell which gasoline came from which station, etc.
EXPLOSIVES
Black Powder - Carbon (=Charcoal), Potassium Nitrate, Sulfur (Low grade explosive)
Explosives are the same as Arson (oxidation reaction) with so much energy it creates a Sonic wave, percussive force.
Low & High Explosives:
Low - Speed of Deflagration (Burning) [Heat, Light & Subsonic pressure]; ie, gunpowder, nitroglycerine, firecrackers. Light it up and it explodes. Nitroglycerin is unstable in liquid form. Molotov Cocktails (more arson). These primers can be a match.
High - Speed of Detonation (Supersonic Shock wave) ie, (Nitroglycerine is found in TNT), TNT, RDX, PETN, Dynamite, Nitrogen & Ammonia based, Plastique.
** Requires an Initiating explosion - primer (burn cord, fuse (a low explosion or an electrical charge)
C-4 is stable until it is fused (energy reaction). ANFO (Ammonium Nitrate Based explosives), Fertilizer based, diesel fuel (Oxlahoma City, first WTC bombing). Water Gels.
Working the Scene:
Go for the point of origin. Looking for the crater, going under the assumption that when it went up and out, hopefully there will be some residue left at the origin. Dig and collect in paint can, but this time FILL ALL THE WAY.
1/2 rinsed with Acetone to get Organic -> FTIR, TLC, GC/MS
1/2 rinsed with Water to get the Inorganic Material -> HPLC
Airport: white filter paper on the briefcase and stuck in machine - ion scan; modified Mass Spectrometer. Looks for specific ions, setup to look for drugs or explosives. Screening tool.
CLANDESTINE LABS
Clandestine Labs - dangerous to the person operating them. 'Kitchens of Death', anyone coming in contact with them or lives near them.
Clandestine labs - mini-chemical labs designed to build and manufacture illegal drugs. Methamphetamine.
More than tripled from 1983 to 1987, California's grew almost 400%
Major hazard: chemical fumes, explosions, fires, booby-traps. Bomb ready to explode (ether)
Booby trap system - use of monofilament line connected to explosive or chemical explosion. Acid into cyanide crystals - Cyanide gas.
Chemicals touching or breathing is dangerous.
Lab locations: rural Rentals, outbuildings, mobile homes; Urban rentals, trailers & Mobilehomes, Motel rooms, rental storage.
HAZMAT - Ether
What to look for:
Strong Unusual Odors
Fortifications
Unusual Traffic
Chemical cans or drums (labels removed or painted over)
Smoking Outside
New High Fences with no visible livestock or animals
What to do:
Secure the area
Narcotics Unit
Fire Department
Call for Patrol Backup
(Subdue the suspect and then do the above)
Detection & Location:
Move Labs Frequently
Any Type of Vehicle may be used
Careless when transporting
Odors/Lab Equipment
- reaction vessels, heating mantles, condensors (attached to reaction vessels), funnels, vacuum flasks, vacuum pumps, separatory funnels.
Purplish liquid -
Light amber in vacuum flasks - washes from reactions
Clear bottles, clear liquids, acids (lye and sodium hydroxides)
Plastic containers for holding acids.
Large barrels, drums with names spray painted to hide contents.
Isolation is chemical chemists best friend (outbuildings, rural locations).
Mobile labs - trailer homes, mobile homes.
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