Fluorescence imaging of latent fingerprints with a cooled charge-coupled-device detector

Images of fluorescently tagged latent fingerprints were obtained using a low power source and a scientifically operated charge-coupled device (CCD) detector. The luminescence of the fingerprints is chemically enhanced with a fluorescent tag, orthophthalaldehyde. The orthophthalaldehyde undergoes a Schiff base reaction with phenyl ring containing amino acids to produce fluorescence emission at ≈446 nm under UV illumination. An inexpensive, portable, low power UV source was constructed utilizing two 4-watt UV fluorescent lamps and appropriate filters. In the past, the use of filtered lamp sources resulted in an appreciable loss in sensitivity compared to laser sources. Preliminary investigations into the use of a low power tungsten filament lamp source for the excitation of NBD chloride tagged fingerprint on paper were also conducted. Sensitive detection by way of a CCD eliminates the need for the use of expensive, high power laser sources in field instruments and provides a wide range of additional advantages over photographic film.