White-light vs. short-wavelength ultraviolet illumination of fingerprints developed with columnar thin films of Alq₃

The deposition of a columnar thin film (CTF) of Alq₃ on partial-bloody fingerprints has recently been shown to yield better development than many traditional development techniques. The Alq₃-CTF-developed fingerprint is illuminated by short-wavelength ultraviolet (UV) light, to take advantage of the luminescence of Alq₃. Experiments were undertaken to test the hypothesis that white-light illumination of Alq₃-CTF-developed fingerprints is inferior to UV illumination. Objective and subjective grading of photographs of 18 Alq₃-CTF-developed fingerprints on brass strongly indicate that white-light illumination is likely to be suitable for comparison; if that fails to yield a strong conclusion, then a photograph taken with short-wavelength UV illumination should be examined by a human. This procedure would reduce not only UV-induced health hazards in the laboratory but also the chance of denaturing potentially useful DNA information contained in the fingerprint.