Fire Scene Evidence Collection Guide
Oils and Greases
Other Viscous Substances
Viscous substances (adhesives, asphalt, tar, wax, grease, stains, and oils) may be present on items collected and may also be found as raw material. The following procedure is for collecting viscous substances in their raw state. In other instances, follow the collection procedures for the item that bears the viscous substance, but make sure that the evidence container you use is leak proof.
To collect viscous substances:
Photograph the substance in place.
Wear new, unused, clean latex or nitrile gloves.
If possible, submit the viscous substance in its original container. Take a picture of the original container or write down the complete description of the container for the laboratory,
Select appropriate packaging for the item (eg: box, paper bag, or plastic bag). If the container may bear fingerprints, take measures (eg: secure with cable ties) to ensure that the container does not rub against the surface of the evidence packaging. Continue with Step 6 below.
If the viscous substance cannot be collected in its original container and the item it is on cannot be collected, use a new, clean eyedropper, disposable pipette, or other suitable tool to collect a sample. Place the sample in a vapor-tight vial or can. Continue with Step 6 below.
Seal the evidence packaging with evidence tape. Initial and date the tape.
Label the evidence packaging with identifying information, including case number, date, exhibit number, a brief description, and your name. DO NOT PLACE EVIDENCE LABELS DIRECTLY ON THE SURFACE OF ORIGINAL VISCOUS SUBSTANCE CONTAINERS.
Store the item in a secure location, such as a locked evidence van or your vehicle, until you are able to transport or mail it to the laboratory.
Laboratory testing of viscous substances:
Viscous substances can be analyzed to determine class characteristics, their general type, and possible source. Chemical analysis can differentiate between certain viscous substances. Waxes may be natural or manmade and instrumental analysis can be used to identify the wax and compare it to a known sample. Greases and oils are petroleum products and can be analyzed instrumentally to determine their chemical composition and propensity to self heat. Fatty acid testing is a destructive specialty test. Be sure to let your laboratory personnel know if you suspect spontaneous combustion.
Crime Scene and Evidence Collection Handbook. Bureau of Alcohol, Tobacco, Firearms and Explosives, 2005.
Gambrel, A.K., and M.R. Reardon. "Extraction, Derivatization, and Analysis of Vegetable Oils from Fire Debris." Journal of Forensic Sciences, 53 (6), 2008: 1372-1380.
Hibbard, R., J.V. Goodpaster, and M.R. Evans, "Factors Affecting the Forensic Examination of Automotive Lubricating Oils." Journal of Forensic Sciences, 56 (3), 2011: 741-753.
Reardon, M.R., L. Allen, E.C. Bender, and K.M. Boyle, "Comparison of Motor Oils Using High-Temperature Gas Chromatography-Mass Spectrometry." Journal of Forensic Sciences, 52 (3), 2007: 656-663.
Schwenk, L.M., and M.R. Reardon. "Practical Aspects of Analyzing Vegetable Oils in Fire Debris." Journal of Forensic Sciences, 54 (4), 2009: 874-880.