Visualisation of fingermarks and grab impressions on fabrics. Part 1: Gold/zinc vacuum metal deposition

Abstract

Vacuum metal deposition (VMD) is a highly sensitive technique originally introduced for detecting latent fingermarks on smooth non-porous surfaces such as carrier bags, plastics and glass. The current study explores whether VMD can be used in the examination of clothing from physical and sexual assault cases in order to visualise identifiable fingermark ridge detail and/or palmar flexion crease detail, thus allowing potential areas to be indicated for DNA swabbing and/or to determine the sequence of events. Four different fabrics were utilised during this study - nylon, polyester, polycotton and cotton, along with 15 donors who ranged in their age and propensity to leave fingermarks, from good to medium to poor as determined by results obtained from test runs using paper and plastic carrier bags processed with VMD. Once samples were collected they were kept for a determined time (1, 2, 3, 4, 5, 6, 7, 14, 21 or 28 days) and then treated using the gold/zinc metal VMD process. From the results, it appears that greater ridge detail is visible on the smoother non-porous fabrics, such as nylon whereas on rougher porous fabrics, such as cotton, only empty prints and impressions, rather than any ridge details, were visible. All fabrics did however allow the development of touch marks that could be targeted for DNA taping thus potentially leading to a DNA profile and possible identification of a suspect.

Visualisation of latent fingermarks on polymer banknotes using copper vacuum metal deposition: A preliminary study

“…These studies applied traditional gold/zinc [12] and silver [13] on dark fabrics to varying degrees of success. Further studies on fabric compared VMD and superglue fuming, which proved VMD to be more effective at developing fingermarks [14].…”

Gold is going forensic

“…The VMD technique was initially adopted as an operational technique for the detection of latent prints on thin polyethylene sheets. Recently this technique has been utilized in non-porous fabrics such as nylon and cotton [43]. Polymer type, among other factors, and previous treatment of the print with cyanoacrylate will affect the VMD conditions required for optimum development [44].…”

Alcimedes 18/5

“…Writing in Forensic Science International, 11 Professor David Bremner and colleagues described their pioneering work, which involved placing the fabric in a vacuum container and then coating with a layer of gold and zinc. Writing in Forensic Science International, 11 Professor David Bremner and colleagues described their pioneering work, which involved placing the fabric in a vacuum container and then coating with a layer of gold and zinc.…”