Electrostatic lifting of marks at crime scenes and the development of the Pathfinder

Abstract

The technique of Electrostatic Lifting (ESL) of dust shoe, tyre and finger marks at crime scenes is well established with scenes of crime examiners. For those who are unfamiliar with the technique, the process is to electrically charge a sheet of black Mylar film with several thousand volts. One side of the film is vacuum coated with aluminium ensuring that the charge is evenly spread on the surface of the film. Once charged the film is strongly attracted to the surface and dust particles forming the mark are lifted perpendicular to the film. The technique allows the finding and recovery of very high quality shoe marks from smooth conducting or non-conducting surfaces and the recovery of marks from textiled surfaces such as carpets, upholstery and wood grained surfaces. At serious crime scenes entire floor areas are systematically covered to reveal shoe marks many of which will not be seen by other means. For this reason each of the five Areas of the Metropolitan Police have access to kits of raised metal floor panels, which for example enable access to a body in a crime scene without disturbing the floor area. the wires. The supposed requirement for as much power as possible to be delivered to the Mylar lifting film is not tenable, as all the machines on the market including the Pathfinder design are capable of delivering enough power to cause the breakdown of Mylar film and arcing if the voltage control is set too high.