1. Fire Basics Forensic Science
Image:
T. Trimpe/B.Brooks

2. Fire Basics The three elements needed to produce and sustain a fire:
Fuel
Heat
Oxygen
When there is a rapid combination of oxygen with a fuel and a noticeable amount of energy is being released, we call this a COMBUSTION reaction.
FUEL
OXYGEN
HEAT

3. Fire Investigation
The first focus of a fire scene must be on photographing and sketching the scene.
An arson investigation can begin immediately without a warrant to enter the property.

4. Fire Investigation Basics
Work from the least damaged areas to the most heavily damaged areas
Document with notes, photographs, and videos Collect evidence (accelerant samples-air tight container, fire items, and other crime scene evidence)
Interview witnesses
Determine the point of origin
Determine the heat source(s)
Hypothesize the reasons for the fire

5. Explosives
An explosion is the product of combustion accompanied by the creation of gases and heat.
There are two type of explosives based on the rate of decomposition:
Low (deflagration)- a very rapid oxidation reaction with a low-intensity pressure wave that can disrupt the surroundings.
High (detonation)- an extremely rapid oxidation reaction with a violent disruptive effect and an intense, high-speed shock wave.

6. Detection and Collection of Explosives
Ion Mobility Spectrometer: screens for the presence of explosive residues.
Collection: the most important step in analysis
All materials must be in airtight containers as to prevent releasing explosive residue.

7. Analysis of Explosives
Examine microscopically to detect particles of unconsumed explosives
Rinse the evidence with acetone to remove any remaining explosives from the debris.
The acetone extract is analyzed using:
Color-spot test
TLC
Gas Chromatography
Most sensitive and reliable
Confirmation Tests
Infrared Spectrometry
X-ray Diffraction