Using Optical Coherence Tomography to Visualise Fingermarks on the Sticky Side of Adhesive Tape

Fingermarks deposited on the adhesive side of tape can be challenging to recover using conventional development techniques, which commonly require physical or chemical treatment of the sample. Optical coherence tomography (OCT) offers a non-contact and non-destructive alternative, providing depth-resolved imaging that can visualise features beneath the surface of the sample. This study investigated the use of swept-source OCT (SS-OCT) for the visualisation of latent fingermarks on adhesive tapes and evaluated its performance under a range of controlled experimental conditions. Natural fingermarks from five donors were deposited on transparent tape, brown packaging tape and red electrical tape and imaged through the non-adhesive backing following approximately 24 hours of ageing. Three experimental studies investigated the influence of tape type, acquisition and repositioning repeatability, and consecutive fingermark depletion. OCT volumes were processed to isolate and visualise the ridge information, and image quality was assessed using a five-point grading system. Repeatability was further investigated using structural similarity index measure (SSIM), mean squared error (MSE), mean region-of-interest intensity and visual image overlays. An additional assessment examined the influence of scan field of view on observable ridge detail. SS-OCT successfully visualised ridge information through the backing of all three tape types included in the main study, with image quality varying between tape types and individual fingermarks. Consecutive acquisitions showed good short-term consistency when the sample remained stationary, while greater variation was observed following repositioning and image registration. Ridge information remained observable across consecutive deposits in the depletion study, and reducing the scan field of view improved the visibility of finer ridge structure. These findings demonstrate the potential of OCT for non-contact examination of adhesive-side fingermarks while preserving the original evidence for possible subsequent analyses. They also highlight the influence of tape properties, acquisition conditions and image processing on the resulting image quality. Further optimisation, automation and validation across more representative forensic samples are required. Nevertheless, the results show that OCT offers a promising approach for accessing fingermark information from challenging adhesive surfaces while maintaining the non-contact and non-destructive advantages that distinguish it from conventional development methods.