"MALDI-CSI": A Proposed Method for the Tandem Detection and Imaging of Human Blood and DNA Typing from Enhanced Fingermarks

Ravell Bengiat, Division of Identification and Forensic Science, Israel Police, Jerusalem, Israel (ravell.bengiat@mail.huji.ac.il)
Katie Kennedy, Biomolecular Research Centre, Sheffield Hallam University, Sheffield, United Kingdom
Cameron Heaton, Biomolecular Research Centre, Sheffield Hallam University, Sheffield, United Kingdom
Yael Herman, Division Of Identification And Forensic Science, Israel Police, Jerusalem, Israel
Carla Oz, Division Of Identification And Forensic Science, Israel Police, Jerusalem, Israel
Michal Levin-Elad, Division Of Identification And Forensic Science, Israel Police, Jerusalem, Israel
Laura Cole, Biomolecular Research Centre, Sheffield Hallam University, Sheffield, United Kingdom
Simona Francese, Biomolecular Research Centre, Sheffield Hallam University, Sheffield, United Kingdom

Blood-contaminated fingermarks are of the utmost importance for the crime-scene investigation in high-profile cases, as they directly connect the suspect to the crime by providing three crucial elements: 1) the identity of the suspect by fingermark comparison; 2) the determination of the human blood in the mark; and 3) the identity of the victim by DNA profiling of the blood. Matrix Assisted Laser Desorption Ionization Mass Spectrometry Profiling and Imaging (MALDI MSP and MALDI MSI), in combination with bottom-up proteomics, have proven to successfully detect and map blood-derived peptide signatures in blood fingermarks with high specificity and compatibility with a number of blood enhancement techniques (BET). In the present study, the application of MALDI MSP and MSI to blood marks has been investigated further in tandem with DNA typing in a scenario simulating blood fingermarks found in crime-scenes. The MALDI MSP was successful in detecting both haem and human specific haemoglobin peptide markers, while MALDI MSI also provided molecular images by visualising haem on the ridge pattern enhanced by BET. The feasibility of successful and subsequent DNA profiling from the recovered fingermarks was also assessed for marks that had undergone enzymatic in situ digestion and MALDI MSI; it was observed that in 73% of the samples analysed, a DNA profile suitable for comparison was obtained. Based on these results, a possible operational workflow has been proposed incorporating the use of a MALDI MS based approach as a confirmatory test for human blood enabling subsequent DNA typing.