NCJ Number
238370
Journal
Journal of Forensic Identification Volume: 62 Issue: 2 Dated: March/April 2012 Pages: 154-164
Date Published
April 2012
Length
11 pages
Annotation
This article presents the basic principles of electrostatic dust-mark lifting (ESL) and describes the associated practices.
Abstract
ESL enables crime-scene examiners to search for and recover footwear dust marks from surfaces. The process of ESL involves placing a sheet of black Mylar film over a dust mark or floor area, then charging the film with several thousand volts. The aluminum coating on Mylar film evenly distributes the electric charge across the film. Once charged, the film is strongly attracted to the surface, and dust particles forming the marks are lifted perpendicular to the film. The ESL technique allows the recovery of high-quality, third-level detail marks from smooth conducting or non-conducting surfaces, as well as the recovery of marks from textile surfaces, although heavy texturing will cause lack of detail. If difficulties are experienced on surfaces with high insulation properties, then an earth bonding kit should be used. This kit connects the earth plate of the ESL machine to either the earth connection of an electrical socket via a static conducting plastic cord or to a water or central heating pipe. This creates many high-tension tracks through the building to the ESL film, greatly reducing the electrical resistance to the charge, because the multiple high-tension tracks are in parallel. In cases where the film is not attracted well to a surface, the film still has a high voltage charge, and the gentle application of a wide insulated roller will cause physical contact with the dust mark, which will lift the mark regardless of whether the suction effect is present. This paper describes in detail the technology of the ESL and the development of the prototype that has made it economically viable for police departments to purchase the devices commercially. 5 figures and 6 references