Study of latent fingermarks by matrix-assisted laser desorption/ionisation mass spectrometry imaging of endogenous lipids Rosalind Wolstenholme, Robert Bradshaw, Malcolm R. Clench and Simona Francese * Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK Received 24 April 2009; Revised 20 July 2009; Accepted 21 July 2009 Identification of suspects via fingermark analysis is one of the mainstays of forensic science. The success in matching fingermarks, using conventional fingermark scanning and database searching, strongly relies on the enhancement method adopted for fingermark recovery; this in turn depends on the components present in the fingermarks, which will change over time. This work aims to develop a robust methodology for improved analytical detection of the fingermark components. For the first time, matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI) has been used to image endogenous lipids from fresh and aged, groomed and ungroomed fingermarks. The methodology was initially developed using oleic acid which was detected along with its degradation products over a 7-day period, at three different temperatures in a time-course experiment. The optimised methodology was then transferred to the imaging analysis of real fingermark samples. Fingermark patterns were reconstructed by retrieving the m/z values of oleic acid and its degradation products. This allowed the three aged fingermarks to be distinguished. In order to prove that MALDI- MSI can be used in a non-destructive way, a simple washing protocol was adopted which returned a fingermark that could be further investigated with classical forensic approaches. The work reported here proves the potential and the feasibility of MALDI-MSI for the forensic analysis of fingermarks, thus making it competitive with other MSI techniques such as desorption electrospray ionisation (DESI)-MS. The feasibility of using MALDI-MSI in fingermark ageing studies is also demonstrated along with the potential to be integrated into routine fingermark forensic analysis. Copyright # 2009 John Wiley & Sons, Ltd. Fingermarks are the result of material from the surface of the skin transferring to another surface on contact. They are distinct from fingerprints, which are control prints where the donor is known and either ink is used or the fingertip is scanned directly. Fingermarks can be composed of endogen- ous and exogenous substances, depending on what the depositing skin has been in contact with. The glands on the palms of the hands and feet secrete different substances from those on other parts of the body; however, in many cases, due to regular contact with other areas, such as the face, fingermarks are composed of substances from both sources, in particular lipids, fatty acids, amino acids, vitamins and water. 1 Fingermarks that are composed of opaque materials, e.g. blood, dirt, paint, are termed patent marks and are easily visible; however, fingermarks that are made of transparent materials, e.g. gland secretions, are termed latent marks and are not easily visible. In order to make a comparison, a latent fingermark must be made visible using a development technique, preferably one that is targeted at the substances present in the mark. In addition, it has been proven that changes in composition occur with time as components degrade. 2 In order to maximise the effectiveness of enhancement techniques, work on fingermark composition has been carried out in several areas; the determination of the range of substances typically found in fingermarks over time is one of these areas. Recent studies have analysed classes of components as a whole, e.g. lipids and proteins, 3 specific members of a class, e.g. proteins, 4 and another study also examined the changes in lipids over time using gas chromatography/mass spectrom- etry (GC/MS). 5 A further study captured images of cyanoacrylate-enhanced marks over time but, on that occasion, did not investigate the chemical changes taking place. 6 Another area of research concerns the chemical imaging of compounds present in fingermarks using fluorescent anti- bodies 7 or advanced analytical techniques such as surface- assisted laser desorption/ionisation time-of-flight mass spectrometry (SALDI-TOF-MS), 8 desorption electrospray ionisation mass spectrometry imaging (DESI-MSI) 9 and attenuated total reflectance Fourier transform infrared (ATR-FT-IR). 3 RAPID COMMUNICATIONS IN MASS SPECTROMETRY Rapid Commun. Mass Spectrom. 2009; 23: 3031–3039 Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/rcm.4218 *Correspondence to: S. Francese, Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK. E-mail: s.francese@shu.ac.uk Copyright # 2009 John Wiley & Sons, Ltd.