No forensic method exists that can reliably estimate the age of fingermarks found at a crime scene. Information on time passed since fingermark deposition is desired as it can be used to distinguish between crime related and unrelated fingermarks and to support or refute statements made by the fingermark donors. We introduce a non-contact method that can estimate the age of fingermarks. Fingermarks were approached as protein-lipid mixtures and an age-estimation model was build based on the expected protein and lipid oxidation reactions. Two measures of oxidation are required from the fingermark to estimate its age: 1) the relative amount of fluorescent oxidation products 2) the rate at which these products are formed. Fluorescence spectroscopy was used to obtain these measures. We tested the method on 44 fingermarks and were able to estimate the age of 55% of the male fingermarks, up to three weeks old with an uncertainty of 1.9 days.

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In the forensic field, knowledge about the time of deposition of semen traces is extremely valuable to law enforcement agencies to assess the relevance of the traces and the validity of witness testimonies. However, currently, no method exists that is able to estimate the time of deposition of semen stains, due to the complex chemistry of the constituents and variation in degradation patterns. Here, we demonstrate a non-contact age estimation method to assess the time of deposition of semen stains using fluorescence spectroscopy. Protein−lipid oxidation reactions were monitored in semen stains over time using protein fluorescence and fluorescent oxidation product signatures to reveal distinctive aging patterns. On the basis of the relative amounts of these fluorescent products and the rate at which they are converted, successful age estimation was achieved up to a value of 16 days, with a median absolute error of 1.7 days. We demonstrate here a new tool that can fill the current gap in intelligence about the age of semen traces that has been challenging the forensic community worldwide.