Integrating Multi-Omics for the Temporal Profiling of Human Biological Traces to Improve Time Since Deposition Estimation

Problem: Time since Deposition (TsD) is the interval between the deposition of a biological fluid at a crime scene and its collection and analysis. Estimating this interval is crucial for crime-scene reconstruction and interpretation of biological evidence. Current forensic methods can reliably identify the donor and the type of biological fluid, but they do not provide robust information on when the trace was deposited. This limits interpretation when the temporal relevance of a trace is central. TsD estimation can support the transition from source-level to activity-level interpretation. However, current approaches remain limited, as most studies focus on dried blood, while saliva and semen are still underexplored, and many rely on single-omics analyses. Since forensic traces are often limited, degraded and non-repeatable, integrated workflows are needed to maximise molecular information from a single trace and improve TsD estimation across different fluids and deposition conditions. Innovation: This project applies an integrated multi-omics approach to study the molecular ageing of blood, saliva and semen for Time since Deposition (TsD) estimation. The workflow aims to recover proteins, metabolites and lipids from the same trace using a unified co-extraction protocol. This allows multiple molecular layers to be analysed in parallel, instead of processing each class separately. By combining these complementary profiles, the project will identify molecular ageing signatures linked to trace deposition over time. These signatures will then be integrated into a multi-omics model to support more robust and reproducible TsD estimation. Standardised Copan swab-based systems will be incorporated to improve recovery, reproducibility and compatibility with forensic workflows. Impact: By combining multiple omics layers from the same biological trace, this project aims to identify biomarker panels with consistent temporal patterns across different fluids, donors, surfaces and deposition times. This approach maximises the molecular information obtained from small, limited or degraded forensic samples, overcoming the current limitation of having to prioritise one analytical method when sample quantity is low. Instead, proteins, metabolites and lipids can be evaluated together to provide a more complete picture of trace ageing. The resulting multi-omics signatures will support the development of quantitative and evidence-based TsD prediction models, strengthening crime-scene reconstruction, improving activity-level interpretation and increasing the evidential value of biological traces.