In collaboration with forensic research teams, we are studying novel techniques to determine the time since the deposition of a fingermark (fingerprint) at a crime scene, because the age of a fingermark is important information for scenario development by forensic and police investigators. The chosen approach is to bind fluorescent entities with a high chemical selectivity to specific molecules in the fingerprints that degrade (or are formed) over time during exposure to atmospheric conditions.
Several relevant molecular markers for age determination of fingermarks have been identified in recent literature, based on advanced analytical techniques such as GC, MS and optical spectroscopy. The compounds degrade over time at different rates, depending on substrate nature and environmental conditions. For specific compounds, effects arising from influence factors that in actual casework are known (donor, substrate, enhancement technique) are found to be larger than the aging effects itself. Furthermore, some factors, such as deposition moment, pressure, temperature, lighting, are typically unknown for a crime scene, which makes their effect also less predictable. Therefore, reliable aging models for fingermarks need to be developed to protect against the unknown factors as their influence cannot be determined in real case work samples.
The main goal of the assignment is to develop a fingermark aging model, consisting of a network of coupled reaction kinetic equations. To this end, the student will perform the following activities:
1) collect all information, available in literature, about the chemical composition of human fingermarks, including its variation between different humans;
2) collect all available chemical degradation mechanisms and degradation reaction kinetics information from literature, including the atmospheric factors, as well as the substrate factors, that play a role in the degradation, as well as the effect of these factors on the degradation kinetics;
3) develop a mathetical model for the degradation of chemical components in fingermarks as a function of time, atmospheric factors and substrate, which can be used to derive the fingermark age from the measured composition of fingermarks;
4) if possible, verify the model experimentally by using advanced analytical techniques on aged fingerprints
Han Gardeniers; E-mail: j.g.e. gardeniers (at) utwente.nl