Recent research by Dr Melanie Bailey from the Department of Chemistry has provided a new method for revealing fingerprints that cannot be developed by conventional means, in collaboration with the Home Office, the Israeli Police and the Netherlands Forensic Institute.
Dr Bailey’s work has recently been published in the journal Analyst and was funded by the EPSRC Pathways to Impact Project. Fingerprints are the most commonly used form of evidence in criminal investigations, despite the introduction of DNA evidence. They result in over 60,000 scenes of crime identifications per year in the UK. A latent fingerprint is invisible to the naked eye and requires some chemical development in order to develop the ridge detail that can be used to identify a suspect. In certain cases, the recovery rate of fingerprints is low due to either the type of surface the fingerprint is deposited on, the age of the fingerprint or the fact that the fingerprint has been exposed to certain environmental conditions.
Dr Melanie Bailey, who lectures on Analytical Chemistry and Forensics, has shown that a technique called secondary ion mass spectrometry can reveal ridge detail in fingerprints that cannot be developed successfully using conventional developers.
Dr Bailey said, “Secondary ion mass spectrometry works by directing a beam of charged particles (ions) at the surface of the sample. This causes molecules to leave the surface of the sample, which are detected in a mass spectrometer. Because the ion beam can be focussed to a small spot size (less than the thickness of a human hair) it can be scanned across a sample to generate a molecular image of that sample.”
Dr Bailey’s study focussed on three examples that have challenged police forces around the globe:
In the first case, fingerprints were deposited on aluminium foil by the Netherlands Forensic Institute successively until the fingerprint became very faint. The fingerprint was developed using superglue (cyanoacrylate), the common procedure for the police, but the fingerprint ridges were interrupted by undeveloped areas, making identification of this faint fingerprint difficult. The fingerprint was then scanned using SIMS (secondary ion mass spectrometry), which managed to fill in the gaps and reveal the ridge detail in the gaps, where the cyanoacrylate had failed.
In a second example, the Israel police deposited fingerprints on the handle of a hand grenade, and tried all their known development procedures to develop fingerprints. It was possible to develop fingerprints up to 24 hours after deposition, but after 24 hours, development of a fingerprint proved impossible. Fingerprints on a hand grenade handle supplied by the Israel Police were scanned using SIMS, and the fingerprint ridge detail was still clearly visible even after 48 hours.
In a third example, fingerprints were buried in soil to replicate burial conditions that sometimes occur in casework. The Home Office tried all their conventional techniques but failed to produce any ridge detail of the fingerprint. However, SIMS was able to reveal the ridge detail.
Dr Bailey added, “These results show that not only are mass spectrometry techniques able to reveal the ridge detail in a fingerprint, but also that they can give clues about what is being left behind in a fingerprint that is not being targeted by the development reagents. This could allow the development of a new, more effective generation of fingerprint developers to be created.”
Dr Bailey, who obtained her PhD in Electrical Engineering from the University of Surrey Ion Beam Centre, is now hoping to secure funding for further research in this area.
Dr Bailey’s article appears in: Analyst, 2013, DOI: 10.1039/C3AN01204B
Title: Enhanced Imaging of Developed Fingerprints using Mass Spectrometry Imaging
The article is available to institutional journal subscribers in both HTML and PDF formats at the following link: http://xlink.rsc.org/?doi=C3AN01204B