Defense Date
2026
Document Type
Directed Research Project
First Advisor
Kimberly Freeman
Second Advisor
Susan Greenspoon
Third Advisor
Catherine Connon
Fourth Advisor
Christopher Ehrhardt
Abstract
With the increasing prevalence of trace DNA in forensic casework, an improved understanding of DNA transfer mechanisms is essential for accurate and reliable interpretation. Passive transfer is defined herein as a type of indirect transfer where biological material is deposited due to routine activity within close proximity to an object. Indirect transfer mechanisms, such as passive transfer, are frequently scrutinized in legal proceedings. This study evaluated passive DNA accumulation under three experimental conditions: passive exposure alone, direct handling at varying durations followed by passive exposure, and direct handling followed by passive exposure in a semi-enclosed environment.
Objects were decontaminated with DNA Away™ and isopropyl alcohol before placement in an active office or vehicular environment for seven days. DNA processing was performed according to validated protocols established by the Virginia Department of Forensic Science (VDFS). Passive exposure alone yielded quantifiable concentrations and detectable profiles, often characterized by allelic drop-out and stochastic effects. Direct handling increased total DNA and allele recovery, but also increased mixture complexity; however, no significant relationship was observed between handling duration and the proportion of unidentified contributor (UIC) alleles. In semi-enclosed environments, cohabitation or passive transfer was detected in two of 12 samples; the primary contributors to mixture profiles were from direct-contact donors and unidentified contributors. The UIC alleles observed may be attributed to background DNA accumulation, consistent with previous studies, as well as to secondary and tertiary transfer. These findings demonstrate that passive DNA is detectable under forensic casework conditions and underscore the importance of caution when interpreting low-level samples and conducting activity-level assessments.
Rights
© The Author(s)
Is Part Of
VCU Master of Science in Forensic Science Directed Research Projects
Date of Submission
4-28-2026