In forensic proteomics, LC-MS is applied to analyze biological evidence from crime scenes, such as body fluids, tissue, hair or food traces. This analysis can help uncover vital information that aids in criminal investigations. Our research is focussed on: sample preparation and method development, body fluid and tissue identification, determining the time since deposition of blood traces, phenotypic characterization of blood, and species identification of trace donors. Our work on body fluid identification focuses on developing advanced techniques to accurately distinguish between different fluids. This is crucial for linking biological evidence to criminal activities, such as rape. We are also investigating methods to estimate the time since blood traces were deposited, which can help establish timelines in criminal investigations. Our research on phenotypic characterization of blood explores the potential of blood samples to reveal physiological traits of individuals, such as sex. Lastly, we are conducting research on species identification of trace donors, which involves distinguishing human from non-human biological material in mixed or contaminated samples.
Our service mainly focuses on identifying the biological source of samples. Using untargeted bottom-up mass spectrometry (MS), we consistently report on the presence of common body fluids such as blood, saliva, semen, vaginal fluid, and urine. We can also detect less common fluids like vomit. To ensure that the identified fluids originate solely from a human donor, we conduct a specialized search to determine whether the peptides are unique to humans or shared with other species. Our species identification process ranges from humans to animals, food sources, and environmental factors.
Our proteomics workflow can be conducted alongside DNA analysis on the same sample, providing a comprehensive biological examination. Typically, for proteomics, we use the supernatant produced during the cell pelleting process, where the pelleted cells are reserved for DNA analysis. However, when a direct extraction protocol is employed, utilizing a lysis buffer that lacks proteases such as proteinase-K, we are able to use the waste fraction from the extraction process for proteomic analysis. This allows us to maximize the utility of the sample without compromising the integrity of either analysis. Forensic samples are frequently contaminated with non-protein materials, such as plastics, making pre-analysis cleanup crucial. To address this, samples are cleaned and digested using the Suspension Trapping (S-Trap) protocol. This process can be performed manually using single-use S-Trap columns or automated with the Andrew Alliance robot and 96-well S-Trap plates. Both approaches ensure effective protein purification and digestion, optimizing the samples for accurate mass spectrometry analysis.