Journal of Forensic Research

Hybrid Techniques in Fingermark Visualization: Combining Spectroscopic and Chromatographic Methods for Complex Substrates

Abstract

Saleh Mansour*

Speculations have been made for some time as to what might happen if hybrid techniques were used in conjunctions to enhance fingermarks. The main consideration to date has been imaging, but there appears to have been no studies of the effects of using spectroscopic techniques on a fingermark that has been developed using a chromatographic technique. This is a significant omission as it is likely that the chemical additives inherent in some substrates would confound the spectral information obtainable from the sebaceous components of a fingermark. Four selected chromatographic techniques, Cobalt-2, Ninhydrin, Sticky Side Powder, and Vacuum Metal Deposition, were used to develop fingermarks on substrates containing chemical additives. Apart from Derek (Cobalt 2), a dark grey background, most of the chemical additives used were either at- or near-IR fluorescent. Fingermarks developed on substrates containing the chemical additives were subjected to three types of spectroscopy: IR, RAMAN, and SERS.

To the authors’ knowledge, this is the first report of successful MALDI enhancement using VMD on marks which have also been enhanced on cellulose substrates. Previous reports have had success using VMD plate-based devices, although these marks had been developed on non cellulose substrates. MAT-irradiated marks and those treated with failed to enhance. This is likely due to the destruction or masking, respectively, of the peptide bonds that are essential for gold enhancement. Of the treatments that did enhance, a threshold was evident at 10 min, as this was the minimum time required for visible development. As discussed above, the signal was found to be on intensity dependent, which is likely a result of the concomitant obliteration of the at-IR fingerprint as the enhancement proceeded. Importantly, however, positive peaks indicative of the presence of sebaceous components were still seen in all but the darkest marks.