Dr Katy Bruce - University of Kent

We all deposit various materials (such as lipids and proteins) on surfaces in varying proportions with every touch. The type and amount of these materials could be used to determine when a fingermark was deposited. This area has attracted extensive attention as researchers try to find a unified model that overcomes the challenge of us all having different fingermark chemistries.  

In the UK, work has centred on fingermark detection and the use of mass spectrometry to interrogate fingermarks. Further afield, vibrational spectroscopies have emerged as methods for studying fingermark chemistries and their changes over time. However, to date there has been no consensus on how to determine the age of a fingermark.  
 
Fingermarks typically contain a complex mixture of large organic molecules with bulky shapes that can orientate themselves in different ways on a substrate; this dimensionality has not yet been investigated. While chemical changes over time have been studied, these have only been able to detect the presence or absence of certain fingermark components, or in some cases, determine their relative quantities. It is highly likely that dimensional changes will occur alongside these chemical changes. Furthermore, the way that a molecule is orientated relative to the substrate it is deposited on may also change with time. This could allow tracking of time intervals within the fingermark chemistry ageing cycle, and therefore provide a unified approach for determining the age of a fingermark.  
 
Traditional vibrational spectroscopic methods give us an overall picture of the chemicals present, yet polarised measurements allow for the wave direction of the incident light to be oriented in a particular direction. Conducting experiments under different polarisation conditions enable us to be sensitive to the size, shape, and most importantly, the orientation of the molecules. This will provide us with new chemical insights and allow us to build new methodologies to determine the time of fingermark deposition.