Visualization of Latent Fingerprint Corrosion of Metallic Surfaces

Abstract

Chemical reactions between latent fingerprints and a variety of metal surfaces are investigated by heating the metal up to temperatures of approximately 600 degrees C after deposition of the fingerprint. Ionic salts present in the fingerprint residue corrode the metal surface to produce an image of the fingerprint that is both durable and resistant to cleaning of the metal. The degree of fingerprint enhancement appears independent of the elapsed time between deposition and heating but is very dependent on both the composition of the metal and the level of salt secretion by the fingerprint donor. Results are presented that show practical applications for the enhancement to fingerprints deposited in arson crime scenes, contaminated by spray painting, or deposited on brass cartridge cases prior to discharge. The corrosion of the metal surface is further exploited by the demonstration of a novel technique for fingerprint enhancement based on the electrostatic charging of the metal and then the preferential adherence of a metallic powder to the corroded part of the metal surface.

The thermal visualisation of latent fingermarks on metallic surfaces

“…Forensic science Latent fingerprints Latent fingermarks Metal Metallic surfaces Enhancement Visualisation A B S T R A C T Recent published research has lead to improved techniques for recovering latent fingermarks from metallic surfaces. The present study corroborates and extends some of the work carried out by Bond [1][2][3], but an alternative mechanism is proposed for the thermal visualisation of fingermarks based on differential oxidation and the production of interference colours that improve contrast. Fingermarks treated at low temperature could be reheated to enhance recovery, but an upper temperature limit occurs beyond which the mark degrades.…”

“…Fingermarks can be recovered by a range of traditional methods such as powdering and cyanoacrylate fuming but these sometimes have limitations and a range of alternative techniques for mark enhancement have been considered over the years. A significant development was made with the recent work published by Bond [1][2][3], and in these papers he reviews earlier research into fingermarks on metals.…”

“…In his initial study Bond [1] examined 40 fingermarks that had been stored at ambient temperature and normal humidity. In the second part of the study, 360 depositions were made on metal samples.…”

Revealing obliterated engraved marks on high strength aluminium alloy (AA7010) surfaces by etching technique

“…In addition many firearms like Ruger pistol [18], Czechoslavakian P-01 pistol [19], S&W Special Airweight Airlite revolver [20] and Brazilian pistols [21] use aluminum alloy frames. Ergal, a hard aluminium alloy (AA7075) is also used for manufacturing firearms [22].…”

Metallographic Etching of Aluminium and Its Alloys for Restoration of Obliterated Marks in Forensic Science Practice and Investigations

“…In addition many firearms like Ruger pistol, Czechoslavakian P-01 pistol, S & W Special Airweight Airlite revolver and Brazilian pistols use aluminum alloy frames. Ergal, a hard aluminium alloy (AA 7075) is also used for manufacturing firearms (Bond, 2008).…”