Human identification through advanced forensic mass spectrometry of blood and fingermarks

Matrix assisted laser desorption ionisation (MALDI) mass spectrometry (MS) has been demonstrated in recent years to be an effective toolbox in the detection and identification of substances of forensic relevance. The goal of this PhD programme was to develop analytical protocols to obtain novel molecular information from two biological sample types; fingermarks and bloodstains. MALDI MS was employed to acquire mass spectrometry profiling (MSP) and mass spectrometry imaging (MSI) data from these two common evidence types to generate biological and chemical information towards a molecular ‗suspect profile‘. The use of MALDI MS to acquire data on the peptide and protein composition of fingermarks, in combination with advanced statistical processing was developed to investigate the determination of sex from fingermarks. A blind validation study was conducted for the robust, multifaceted identification of human and animal blood, other human biofluids and interferent substances from a large sample set of stains and fingermarks. MALDI MS was employed in combination with a ‗bottom-up‘ proteomic approach for the determination of biological matrices through the identification of proteotypic peptides. MALDI MS was also utilised for the determination of a subset of haemoglobin variants in human blood, through the detection of proteotypic peptides, employing a ‗bottom-up‘ proteomic approach. The detection of haemoglobin variants in blood encountered at a crime scene has implications towards associative evidence of the presence of an individual, which grows in significance the rarer (and less prevalent) the variant. The application of these three techniques towards these two biological matrices, and the validation data acquired for each, demonstrates their analytical capabilities. In all cases they have been demonstrated to be compatible with visualisation techniques (both fingermark enhancement techniques and blood enhancement techniques, respectively), showing potential for their integration into the current operational workflows for both fingermarks and blood. In conclusion, although only demonstrated under laboratory controlled conditions, MALDI MS shows promise towards the future analysis of these biological matrices within evidence recovery and investigative workflows, when specific molecular information may be sought.