Chemical profiling of fingerprints using mass spectrometry

Fingerprints are widely used in forensic science for individualization purposes. However, not every fingermark found at a crime scene is suitable for comparison, for instance due to distortion of ridge detail, or when the reference fingerprint is not in the database. To still retrieve information from these fingermarks, several studies have been initiated into the chemical composition of fingermarks, which is believed to be influenced by several donor traits. Yet, it is still unclear what donor information can be retrieved from the composition of one's fingerprint, mainly because of limited sample sizes and the focus on analytical method development. It this paper, we analyzed the chemical composition of 1852 fingerprints, donated by 463 donors during the Dutch music festival Lowlands in 2016. In a targeted approach we compared amino acid and lipid profiles obtained from different types of fingerprints. We found a large inter-variability in both amino acid and lipid content, and significant differences in L-(iso)leucine, L-phenylalanine and palmitoleic acid levels between male and female donors. In an untargeted approach we used full-scan MS data to generate classification models to predict gender (77.9% accuracy) and smoking habit (90.4% accuracy) of fingerprint donors. In the latter, putatively, nicotine and cotinine are used as predictors.

For over 100 years, fingermarks have been used for individualization purposes. Even today, fingerprint evidence is widely used in forensic science. A fingerprint originates from contact between a bare fingertip and a surface and mainly consists of eccrine and sebaceous excretion. Because the excretory glands are only located on the friction ridges and not in the furrows, the excretion can be left behind on the surface in the distinctive fingerprint pattern. Comparison between a fingermark found at a crime scene and a reference fingerprint can lead to individualizing the perpetrator. However, not every fingermark found at a crime scene can be used for individualization purposes. It may be the case that the reference fingerprint is not in the database, or that the fingermark is of poor quality in terms of ridge detail, for example due to distortion of the fingerprint pattern. Therefore, there is great interest among forensic investigators in techniques that can still retrieve basic donor information from these kinds of fingerprints.