READ: Glass and Soil Evidence

Collection and Preservation of Soil

Because of the likelihood of soil samples varying even within a small radius of the area of interest of the crime scene, it is important that multiple samples be collected for the purpose of soil analysis and comparison. The soil samples should be collected at various intervals within a 100 yard radius of crime scene as well as from all possible alibi locations. In general, the soil samples needed for soil analysis are taken from the top layers of soil as that is where soil is almost always picked up from and tracked to other locations. An exception to this is if a body was buried; deeper soil samples will need to be taken for a soil comparison in this context.

Soil Analysis Collection Guidelines

• Always allow soil samples to air dry before packaging them to avoid growth of mold in the sample.

• All samples should be labeled with the date, time, location, person who collected the sample and any other pertinent identifying information.

• Each suspect soil sample should contain about 1 tablespoon of soil and comparison soil samples from the areas of interest should contain about 3 tablespoons of representative soil. Comparison samples should be taken from the crime scene, as well as all areas indicated in the suspect's alibi.

• Loose samples of dirt/sand can be swept into a clean piece of paper, folded, taped and labeled for analysis at the lab.

• Soil should not be removed from clothing or shoes of a victim until they are in the crime lab. When soil is present in tires, shoes, or other objects, the layering should be preserved as much as possible to help establish a timeline.

• When collecting impressions from shoes or tire treads, the area must first be photographed, then sprayed with a fixative to harden the impression. The final step is to obtain a plaster cast of the impression for lab examination.

Georgia Virtual, Forensic Properties of Glass and Soil Evidence, CC BY-NC-SA 3.0