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Fingerprinting – where chemistry and forensic science can come together

By William Peveler, on 26 May 2014

Researchers at Hanyang University in Seoul have recently published work in Nature Communications describing a new polymeric material they have developed, which is capable of mapping sweat pores in the human fingerprint at high resolution (doi). The polymer changes colour and becomes fluorescent when exposed to moisture (hydrochromic), even at low concentrations, and thus when a finger mark is deposited on a sample of the material, a point pattern fluorescent image is generated which can be recorded with fluorescent microscopy. The researchers go on to compare a selection of these to ninhydrin-stained latent marks, also exhibiting pore structure, to show a good match. They argue in their paper that the analysis of sweat pores in marks, rather than the typically used ridge structures, means that an incomplete or indistinct mark can still be used to generate a match if sweat pores are available. They neglect to discuss, however, the availability of sweat pore location information in lifted marks; and all their analysed marks were deposited directly onto the polymer itself or digitally scanned, rather than a more realistic examination of real world marks against their material as a reference.

It is exciting to see work with a strong forensic component featuring in such a high impact publication, beyond the normal forensic science journals, and this is partly due to the high quality chemistry content regarding the design and synthesis of their new polymeric material, and an in depth analysis of its hydrochromic properties. There is a good chance that this work will be widely covered in the popular-science and lay media too, due to the all-important CSI effect (e.g. here). However, are the results reported actually important forensically – or are they merely a handle to boost a good supramolecular chemistry paper to being a superstar nature paper? As the Korean authors admit, the materials they describe are not entirely novel; this class of polymers was first posited for mark development by an Australian group led by Tahtouh in 2011 (doi). However this initial research was published in Forensic Science International, where no doubt it escaped the notice of much of the chemical sciences and of the wider establishment, despite its forensic rigour in investigating the application of these polymers as mark developers on a variety of surfaces.

So maybe there are two messages that can be taken from this paper. Firstly, the mapping of sweat pores within finger marks may be an important part of dactyloscopy in the future, with the advent of new materials such as these allowing easy collection of sweat pore information.

However, a second message to take away might be that; if, as a forensic scientist you’ve stumbled across what you feel might be the next big thing, maybe get together with a chemist/physicist/etc. and big up the background science, and offer it to a journal beyond the forensic sphere. For example FSI has an impact factor of ~2.3 whereas Angewandte Chemie Int. Ed. scores ~13.7, and as evidenced by a recent spate of fingerprinting related papers they have published, the latter loves a good forensic science article. The chemists carrying out this fundamental research into novel development agents and materials often do not understand the intricacies and limitations of day-to-day practitioner case work, and the forensic scientists working on minor improvements to their well honed but basic techniques often do not look at the high-level theoretical work going on to further their ideas –it’s time to get the two together and then maybe there could be a lot more Nature papers on forensic science.

Many thanks to Helen Earwaker for informative discussion. Lee et al. 2014 “Hydrochromic conjugated polymers for human sweat pore mapping”. Nature Comms, 5, 3736 – is available as an open access paper from dx.doi.org/10.1038/ncomms4736.