Fingerprint detector

Special particles in security inks that were developed to foil forgers might now help catch all kinds of criminals.

Special particles in security inks that were developed to foil forgers might now help catch all kinds of criminals thanks to the work of University of Technology Sydney (UTS) fingerprint researchers in collaboration with the Australian Federal Police (AFP).

Researchers from the Centre for Forensic Science in the UTS Faculty of Science have found that these particles, designed to show up under infrared light, can also be used to reveal fingerprints on ‘difficult’ surfaces, like Australia’s polymer banknotes.

Graduating honours student Elicia Bullock and principal supervisor Dr Philip Maynard are the first to assess the potential of so-called anti-Stokes materials in fingerprint detection – results that were recently reported to the International Fingerprint Research Group Conference in Canberra.

Ms Bullock, an international student from Canada, told experts from the USA, Europe and Australia that commercially available anti-Stokes materials could be successfully substituted for traditional reagents in a range of fingerprinting techniques.

Director of the Centre for Forensic Science, Professor Claude Roux, said fingerprint detection using luminescence under ultraviolet, blue or green light was generally very effective but forensic investigators could be frustrated trying to show up fingerprints on surfaces which also luminesce under similar light conditions.

‘Fluorescent dyes and other materials commonly used in commercial products and packaging can interfere with the standard luminescent fingerprint reagents, as can printed surfaces with complex patterns like banknotes.

‘The rare earth anti-Stokes materials, also called up-converters, were worth investigating because they luminesce under light at the opposite end of the spectrum. Up until now their chief use has been in adding security features to documents, paper banknotes and identity cards.

‘Luminescence under infrared light is unusual in both natural surfaces and consumer products, which meant there was the potential to beat the interference problems experienced with normal reagents.’

In the UTS/AFP study, latent fingermarks were deposited on six non-luminescent and six luminescent surfaces, including Australian polymer banknotes, and developed with up-converters using a variety of techniques including dry powdering, sticky-side powder (wet powdering) and staining after superglue fuming.

The results demonstrated that up-converters had ‘enormous potential’ in fingerprint detection. However the researchers believe more work is needed before the use of anti-Stokes materials becomes a routine method in forensic labs.

‘At present, commercially available anti-Stokes pigments are relatively expensive and are manufactured in small quantities for specific applications,’ Ms Bullock’s said. ‘More research is required to explore the potential and practical application of these pigments for routine fingerprint detection purposes.’