New non-destructive technique for chemically analysing fingerprints collected from crime scenes
UK researchers have demonstrated a new non-destructive method to collect and chemically interrogate fingerprints left at the scene of a crime.
Camilla Ricci and Sergei Kazarian from Imperial College London and Steve Bleay from the Home Office Scientific Development Branch, showed that a commercially available gelatin that is already used to gather forensic samples, such as prints that have been visualised by ’powdering’ at the scene, can be used to lift unpowdered ’latent’ prints from a wide range of surfaces. The prints can then be analysed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to reveal chemical information about any residues present in the print.
’This is the first time that chemical images of latent fingermarks collected with gel lifters from different surfaces have been obtained,’ the researchers report. Furthermore, by varying the angle at which the spectroscopic images are taken it is possible to obtain spectra from different depths within the fingermarks, giving a three-dimensional depth profile of surface contaminants, adding to the technique’s potential versatility as a forensic analytical tool.
Ricci and colleagues showed that a particular gelatin product, called BVDA Gelatin Lifter, could be used to collect fingerprints from a range of surfaces, including a mug handle and computer screen. The marks could then be analysed by ATR-FTIR, clearly demonstrating the presence of chemical residues in the marks - in this case naturally-occurring lipids.
The findings demonstrated that the lifting medium did not interfere substantially with the imaging of the spectral features of the residue left by the fingerprint. ’In addition, the gel lift approach is a non-destructive method as the gel can be easily removed from most surfaces, both porous and nonporous, without destroying them,’ the team reports. ’The non-invasive nature of this spectroscopic technique also allows subsequent use of samples for further analysis.’
Tim James, a forensic scientist at the University of Teesside, UK, said that the work was ’interesting’ but that the method would appear to have limited practical use in actual scene of crime work. ’The technique would have to be decided to be used early as part of a forensic strategy as you would not know a fingermark was present prior to lifting and the speculative taping of large areas would be impractical and may not be the best technique to utilise,’ James told Chemistry World.
James added, however, that ’without such research, techniques would not be developed which can be refined to a point where they become a practical and everyday analytical process to aid in the enhancement of crime scene marks and hence the detection of crime.’
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C Ricci et al, Analytical Chemistry, 2007, DOI: 10.1021/ac070580j