Determining Time Since Deposition of Epithelial Cell Samples Using Intrinsic Fluorescence Signatures

The goal of this project is to develop a new method for determining the time since deposition for epithelial cell populations that can be used for a variety of sample types including touch or trace biological evidence. Establishing the age of evidentiary samples is a critical need for caseworking laboratories as it can provide probative context to DNA profiling results. Currently, few methods have been described for determining the age of epithelial cell samples and, of those methods, none have been validated for casework. To address this challenge we have developed a novel workflow that analyzes the autofluorescence and morphological signatures of cell populations that varies with time following sample deposition. Using predictive algorithms based on a reference dataset, the time since deposition can then be estimated for unknown biological samples. The primary advantage of this method for forensic casework is that all aspects of the workflow are high-throughput and inherently non-destructive which is ideal for evidence samples since these are typically compromised and low in template quantity. Our specific aims include (1) survey of autofluorescence and morphological signatures for saliva epithelial cell populations and touch/trace epidermal cell populations. (2) development of predictive classification algorithms for determining time since deposition in epithelial cell populations, (3) error assessments using mock casework samples, and (4) cross platform integration of signatures with other microscopic and/or benchtop Instrumentation. The expected outcomes for the project include peer-reviewed manuscripts describing the workflow, results from validation tests, and the applications of this method for forensic casework. This research will provide a fast, high-throughput. and non-destructive front-end analysis techniques within a forensic DNA caseworking laboratory that can enhance the probative value of many types of biological samples. Note: This project contains a research and/or development component, as defined in applicable law, and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14). CA/NCF