Nanoscale Imaging and Chemical Analysis of Extracellular DNA in Trace Evidence Samples

• NCJ Number: 304644
• Date Published: 2022
• Author(s): Vamsi K. Yadavalli; Christopher J. Ehrhardt
• Length: 13 pages
• Grant Number(s): 2017-DN-BX-0186
• Agencies: NIJ-Sponsored

Annotation

This is the Final Report of a project that sought to understand the physical and chemical nature of trace-cell deposits transferred by touch or contact, including the differences between various cell types and the spatial and biochemical context on the cell surface.

 

Abstract

Using high-resolution, nondestructive tools, the project provided a unique vision of the cell surface, its nanoscale morphology, its mechanical properties, and the presence of specific cell surface signatures, including eDNA. These spatial and temporal signatures will lead to a better understanding and handling of cellular samples collected as evidence, leading to the development of ultrasensitive tools for cell attribution and precise analysis of touch and contact DNA. This research has led to strategies to optimize the recovery and profiling of trace DNA from an aged, degraded, and/or low template sample. This was done by providing an understanding of the source (epithelial cells) and nature of DNA, i.e., whether it is free or anchored to the surface, transferred through touch or contact. To date, these interdisciplinary biophysical and biochemical tools have not been used in forensics. This project developed methodologies for rapid, ultrasensitive, and non-destructive sample analysis in forensic applications and an enhanced understanding of key biological properties of extracellular DNA and cell types relevant to forensic casework. The number of touch and contact samples being collected and submitted to case-working units remains a problem, so better ways of handling such evidence and understanding the fundamental science behind them are needed. 4 figures and a listing of project reports