The forensic exploitation of fingermark chemistry: A review

The substances deposited from the fingertip onto a surface during contact between them represent a highly complex range of chemicals that can be exploited in a variety of ways in a forensic investigation. An overview is given of the multitude of chemicals that have been detected in fingermarks, including those occurring in endogenous sweat, metabolites of ingested substances, and exogenous substances picked up on the fingertip. Changes in chemistry that may occur between deposition of the fingermark and its subsequent forensic analysis are discussed, with particular reference to the ways in which these changes have been considered as a means of dating fingermarks. The ways in which fingermark enhancement reagents utilise the different chemicals present to reveal ridge is reviewed, together with how different classes of chemical can be sequentially targeted to optimise the number of fingermarks recovered. A field of increasing interest is the use of advanced analytical techniques incorporating mass spectrometry and imaging capability to simultaneously obtain additional contextual information about the donor of the mark whilst visualising the fingermark ridge pattern. Examples are given of how such information can be applied in forensic investigations. It is concluded that an extensive ‘tool kit’ of fingermark enhancement processes is already available to utilise the different chemicals present, and the advances that can be made in this field using conventional approaches are limited. There is, instead, significant potential to utilise analytical techniques to forensically exploit the chemical information within fingermarks but there are also significant barriers to their implementation in this way.