Lecture Arson Analysis of Fire Debris. Arson is defined as purposely setting fire to a house, building or other property . . Rules of a Fire’s Origin. 1997 Arson Statistics. The fire burns up and out (v-pattern). The presence of a combustible material is needed.
Arson is defined as purposely setting fire to a house, building or other property.
The fire burns up and out (v-pattern).
The presence of a combustible material is needed.
The fire needs fuel and oxygen to continue.
The fire’s spread will be influenced by air currents, walls and stairways.
Flash point - The temperature at which a particular flammable liquid
gives off vapors (vaporizes) and therefore can ignite.
The ignition temperature is the temperature required for a liquid to
continue to emit vapors that can sustain
A flammable liquid in its liquid state will not burn. It only will
ignite when it vaporizes into a gaseous state. All flammable liquids
give off vapors that can ignite and burn when an ignition source such as
a lighted cigarette or spark is present.
Point of Origin (POO).
Liquid materials are commonly used because of ease of ignition and familiarity of use.
Accelerants are nearly exclusively derived from hydrocarbons.
Straight chain hydrocarbons are the backbone of the oil industry.
Hydrocarbons are molecules made up of the elements hydrogen and carbon.
Octane is a term familiar to all. It consists of a hydrocarbon having 8 carbons.
1. Light petroleum distillates (LPD)
3. Medium petroleum distillates (MPD)
5. Heavy petroleum distillates (HPD)
A refined petroleum mixture of the C4 through C12 range.
Produced from crude oil using the ‘cracking and reforming’ production method.
All brands and grades of automotive gasoline fit within this category.
Produced by distilling crude oil.
Made from the C9 through C16 range of hydrocarbons.
Class representatives: kerosene, jet fuel, and lamp oils.
Produced by collecting and recombining certain fractions of distilled crude oil.
Made from a wide range of hydrocarbons.
Class representatives: brush cleaners, thinning agents, strippers, products for home, automotive and industrial use.
Dogs can detect 0.01 mL of 50% evaporated gasoline 100% of the time.
0.01 mL is about the size of a thousandth of a drop.
Taking samples from the wrong places or materials
Ineffective sample preservation techniques
No comparison samples
Not maintaining an evidence “chain of custody”
A gas chromatograph is coupled to a mass selective detector.
We can look at this in four different ways...
No ignitable liquids were ever used
Ignitable liquids were used to start the fire, but have been totally consumed.
Ignitable liquids are still present; however, not in the collected sample.
Ignitable liquids are still present in the collected sample; however, they are too dilute to be detected.