Fluorescent metal organic frameworks for the visual enhancement of latent fingermarks.

Lanthanide-based (Eu and Tb) metal organic frameworks (MOFs) synthesized in this work are highly fluorescent crystalline structures that form through a self-assembly process in an aqueous environment. Various bio-organic molecules, including proteins and amino acids, can act as inducing agents for this process. The fact that these components are present in fingermark secretions, in combination with the excellent luminescent properties of the MOFs, create a visualisation method for (latent) fingermarks. The aqueous MOF precursor solutions are not ideal for the visualisation of latent fingermarks on non-porous surfaces, such as aluminium foil and glass. However, they offer a simple, non-toxic, long-lasting and effective approach for the visibility enhancement of fingermarks treated with cyanoacrylate fuming on aluminium foil and glass and latent fingermarks on the adhesive side of a transparent tape. The luminescent properties of MOF-treated fingermarks persevered for at least 12 months, providing great alternative for commonly used organic dyes such as Basic Yellow 40 and Gentian Violet. In this communication we evaluate the applicability of the proposed method for the forensic fingermark workflow.

Performance of 1,2-indanedione and the need for sequential treatment of fingerprints.

The use of 1,2-indanedione-ZnCl2 (IND-Zn) for the visualisation of fingermarks on porous materials has been widely accepted. The use of the reagent in comparison with others has been well described. To what extent IND or IND-Zn reacts with amino acids, in comparison to ninhydrin, has not been described to date. In this technical note we describe the analysis of amino acids with LCMS with the purpose of understanding the reactivity of ninhydrin, IND-Zn and the sequence thereof. The consumption of amino acids by these visualisation reagents is a feature we propose to use for calculations on the reactivity of these reagents. By using recently developed methods for the quantification of amino acids, we determined the consumption of these entities by visualisation reagents. We show that the differences in reactivity between IND and ninhydrin are not as big as the differences between 1,8-diazafluoren-9-one (DFO) and ninhydrin. We also show that it is of great importance to use IND-Zn and ninhydrin in sequence, in order to fully consume the amino acids present in fingermarks.

Detection and mapping of illicit drugs and their metabolites in fingermarks by MALDI MS and compatibility with forensic techniques.

Despite the proven capabilities of Matrix Assisted Laser Desorption Ionisation Mass Spectrometry (MALDI MS) in laboratory settings, research is still needed to integrate this technique into current forensic fingerprinting practice. Optimised protocols enabling the compatible application of MALDI to developed fingermarks will allow additional intelligence to be gathered around a suspect's lifestyle and activities prior to the deposition of their fingermarks while committing a crime. The detection and mapping of illicit drugs and metabolites in latent fingermarks would provide intelligence that is beneficial for both police investigations and court cases. This study investigated MALDI MS detection and mapping capabilities for a large range of drugs of abuse and their metabolites in fingermarks; the detection and mapping of a mixture of these drugs in marks, with and without prior development with cyanoacrylate fuming or Vacuum Metal Deposition, was also examined. Our findings indicate the versatility of MALDI technology and its ability to retrieve chemical intelligence either by detecting the compounds investigated or by using their ion signals to reconstruct 2D maps of fingermark ridge details.

A model study into the effects of light and temperature on the degradation of fingerprint constituents.

Determining the order of events in a criminal investigation can be crucial in many ways. Although the use of fingermarks is one of the most important forensic tools as a modality of individualisation, placing them in time is a long lasting difficulty. In the study presented in this paper we describe the effects of light and the temperature on depositions of standard solutions containing squalene and cholesterol on paper. The results obtained give a clear view on what type of processes take place during a temperature and a light influenced degradation of the two materials in this study. Using well known methods for the determination of reaction constants it was determined that the degradation mechanism of cholesterol is following a radical route, where the decay of squalene is more affected by temperature.

Enhanced imaging of developed fingerprints using mass spectrometry imaging.

Latent fingermarks are invisible to the naked eye and normally require the application of a chemical developer followed by an optical imaging step in order to visualize the ridge detail. If the finger deposition is poor, or the fingermark is aged, it can sometimes be difficult to produce an image of sufficient quality for identification. In this work, we show for the first time how mass spectrometry imaging (in this case time-of-flight secondary ion mass spectrometry, ToF-SIMS) can be used to enhance the quality of partially recovered fingermarks. We show three examples of how chemical imaging can be used to obtain enhanced images of fingermarks deposited on aluminium foil, glass and the handle of a hand grenade compared with conventional development techniques.