Forensic Chemistry

Marks

Footwear, tyre or toolmarks from a crime scene can be compared to the physical and unique characteristics of a shoe, crowbar or a tyre. The examination of physical marks and impressions, unlike the analysis of trace materials such as fibres, paint and glass, can provide conclusive evidence to connect two items. Comparisons are made by comparing size, patterna dnd egree of wear as well as any unique damage features.

Latent marks, which will require enhancement to reveal their presence, are sometimes produced as a result of the manufacturing process. Cellmark undertakes the analysis of footwear marks in blood in-house. These marks can be revealed by the use of specialised lighting techniques and chemical enhancement. Another example is the extrusion of plastic to form a thin film which is then made up into plastic bags. This technique has been used to connect a number of "bin" bags used to wrap a female's body, which had been dumped into water, to bags found in the home of a suspect.

The use of chemical techniques to enhance the quality and contrast of a variety of marks. From scene examination to the reconstruction of events, even when there have been attempts to clean up, to the identification and comparison of footwear marks and enhancement of fingerprints.