Recording living and postmortem friction ridge patterns using image processing and a fiber-optic-inspired total...

Recording friction ridge patterns is a critical step in personal identification, as only clear impressions can be reliably compared with database records. This study presents two approaches-image processing and a fiber-optic-inspired total internal reflection method (FOM)-and compares them with frustrated total internal reflection (FTIR), ink, and powder methods to identify a simple and reliable workflow for forensic evidence collection. The results indicate that no single method is suitable for all fingerprint conditions; instead, a combination of complementary techniques is required. The recommended workflow begins with photographic documentation of the native friction ridge appearance for subsequent image processing. In practice, fingerprint recording is primarily performed using the FOM, supplemented by powder when necessary. The FOM provides a simple and practical approach for visualizing ridge detail using minimal equipment and shows reduced interference from wrinkles, allowing more continuous ridge structures to be observed. However, its performance is reduced in hyperkeratotic fingerprints, which can be improved by combining the method with powder. Image processing also demonstrates considerable potential, and in some cases, processed images are comparable to those obtained using contact-based methods. When contact-based techniques fail to reveal ridge detail, image processing may still provide sufficient information for identification.