Non-invasive, optical latent fingerprint acquisition from cartridge casings: A first feasibility study using a laser-scanning confocal microscope

Technologies and partly automated systems for the support of forensic criminalistic examinations are currently an important field of research with rising importance. Specifically the application of contact-less, optical sensors and subsequent signal processing techniques for the acquisition and enhancement of latent fingerprints from nonabsorbent surfaces are at present important fields of research. In this work a series of tests is performed to investigate the general feasibility of a laser-scanning confocal microscope for the task of latent fingerprint acquisition on cartridge casings. For our first evaluation we are using flattened as well as original shaped cartridge casings and we are scanning previously determined regions with latent fingerprints. Fingerprints have been provided by three different donors and cartridges of three different manufactures are used. The prints are applied on the cartridges after firing and non aged fingerprints are used. According to an existing suggested benchmarking scheme we are using a differential image approach to judge the sensors capability of acquiring these traces. No automated feature extraction is done yet and the quality of the results is assessed in a quantitative and a qualitative fashion. Furthermore, we will provide some very first enhancement experiments using signal processing techniques for enhancing the captured fingerprint representation. Even though our test set is limited and the results are of preliminary nature we provide a proof of concept that the sensor is able to capture the desired traces. Additionally, we are giving an outlook what techniques should be addressed in future work to design an imaging system for acquisition and extraction of latent fingerprints on cartridge casings.