The Alabama
Department of Forensic Sciences Fire Debris section of the Chemistry Discipline
operates in one laboratory location to include: Birmingham/Hoover.
The Fire
Debris section is charged with the mission of identifying the presence or
absence of ignitable liquids. To accomplish this mission the fire debris
section utilizes a variety of extraction methodologies and analytical
instruments. Evidence submission types include, but are not limited to,
liquids, carpets, burned debris, wood, plastic, and fabrics.
Evidence Documentation
Arson must be regarded as a
possible, if not probable, cause of every fire investigated. The value of
physical evidence depends upon the proper documentation, collection, and
preservation of the evidence from the time of its initial discovery and
collection to its subsequent examination and analyses.
Movement or collection of the
physical evidence should be avoided until the item has been photographed and
documented as to location. Documentation can best be accomplished through notes
at the scene, written reports, sketches, and diagrams with accurate
measurements and photography. The diagramming and photography should always be
completed before the physical evidence is moved or disturbed.
Evidence Collection
1. Ignitable liquid samples - When a liquid sample is found at
the scene, a sample of the liquid should be submitted for analysis.
Ignitable liquids found at the scene (charcoal starters,
etc.) should be collected for comparison standards.
The liquid should be collected in a small vial with
screw-on caps made of phenolic resin, polyethylene, or Teflon. Sterile cotton
balls or gauze pads may be used to adsorb the liquid sample if a vial is not
available. The cotton balls or gauze pads are subsequently sealed in a new,
unused metal paint can. An unused sample of cotton balls or gauze pads should
be submitted to the laboratory for comparison.
Never submit
more than a half of cup of liquid to the laboratory for analysis.
2. Ignitable liquids absorbed on porous materials - Ignitable
liquids may be trapped in porous materials such as a concrete floor.
If the concrete floor can not be removed, an absorbent
material such as lime or flour may be spread over the area, allowed to stand
for 20-30 minutes and then collected for analyses.
Clean tools and containers for the recovery step must be
used since the absorbent may be easily contaminated.
A sample of the unused absorbent should be preserved for
analysis as a comparison sample.
3. Ignitable liquids absorbed by solid materials - Ignitable
liquids may be absorbed by solid materials at the fire scene. A few examples of
solid materials that may be collected at the fire scene are: wood, carpet,
carpet padding, furniture, concrete, cloth material, clothing, shoes, etc.
4.Soil - Soil samples should be submitted to the laboratory as
soon as possible. Bacteria in soil can “eat” petroleum-based products.
It has been our experience that positive samples after six
weeks of storage were negative for petroleum-based product.
Note: Collection
of physical evidence after the fire scene has been released requires a search
warrant.
Evidence Containers
1.Metal cans: quart, one-gallon, five-gallon
2.Nylon fire debris bags
DO NOT use plastic bags
since ignitable liquids will pass out through the plastic, and never use paper
bags or envelopes.