Hidden signatures: new reagents for developing latent fingerprints.

Aldehydes substituted with a quaternised pyridinium or quinolinium ring have been investigated for the development of latent fingerprints. Two routes were developed to a novel in situ formed azacyanine dye. This dye might form in the fingerprint where reagents are concentrated but does not form appreciably in solution experiments as evidenced by the lack of an absorption band at 600 nm. N-Alkyl and N-aryl substituted benzimidazole-2-carboxaldehydes give stable fluorescent fingerprints.

Identification of oxidation products of squalene in solution and in latent fingerprints by ESI-MS and LC/APCI-MS.

An investigation was carried out to identify oxidation products of squalene (SQ) in latent fingerprints. Oxidation products of SQ incubated in solution with Rose Bengal as a photooxidizer were isolated by semipreparative HPLC-UV and identified by direct infusion ESI-MS and flow injection APCI-MS. Squalene hydroperoxides ranging from squalene monohydroperoxide (SQ-[OOH]) to SQ-[OOH]5 were identified together with SQ epoxide. SQ-[OOH] was the main oxidation product. An LC/APCI-MS method was developed and used to monitor the fate of SQ in solution and in latent fingerprints and the formation of SQ-[OOH] and SQ epoxide. SQ-[OOH] and SQ epoxide were detected in freshly deposited prints but increased markedly after 1 day and continued to increase up to 5 days after print deposition. By day 7, these substances could no longer be detected in prints. SQ was rapidly depleted from prints such that by day 7 it was no longer detected. A similar pattern was seen for SQ stored in the light in dichloromethane but with a slower formation of SQ-[OOH] and SQ epoxide. The oxidation of SQ in solution in the presence and absence of photooxidizer was shown by TLC to proceed as follows: SQ-->SQ-[OOH]+SQ epoxide. SQ-[OOH]-->SQ-[OOH]2-->SQ-[OOH]3-->SQ-[OOH]4+SQ-[OOH]5, with oxidation being more rapid in the presence of photooxidizer. SQ-[OOH]4 and SQ-[OOH]5 could still be detected at 20 days in a solution of SQ aged in solution in the absence of photooxidizer. The oxidation products of SQ should make suitable targets for development of new reagents for visualizing latent fingerprints in forensic science.

Changes in the lipid composition of latent fingerprint residue with time after deposition on a surface.

The work described in this report was focused on generating increased knowledge of fingerprint chemistry, particularly the composition of a latent fingerprint at the time it is deposited, and the chemical changes in lipid components that occur over time. Fingerprints from five male donors (aged 25-34 years) were collected and aged under controlled conditions. The prints were then sampled at set intervals, solvent extracted with dichloromethane, co-derivatized with MSTFA and analyzed by gas chromatography-mass spectrometry (GC-MS). It was shown that there was loss of squalene from prints stored in the light or in the dark. Loss was more rapid in the light, with squalene in prints from some donors not detected after 9 days storage. For these same donors, squalene was still detected after 33 days storage in the dark, but at much lower levels than in fresh prints. For saturated fatty acids (tetradecanoic, palmitic and stearic acid) there was a trend towards an increase in levels of these substances during storage (up to about 20 days) followed by a decrease back to original levels or below. This was the case for samples stored in the light or in the dark. For palmitoleic acid, a similar trend was seen. For oleic acid, this trend was seen for samples stored in the dark. For samples stored in the light the general trend was a decrease in level over the storage period (up to 33 days).