Author: Claire Mercer
Mercer, Claire, 2025 DNA Transfer Between Exhibits, Evidence Bags and Workspaces, Flinders University, College of Science and Engineering
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Recent advancements in DNA technologies used within forensic science allows genetic information to be gained from smaller amounts of cellular material than was previously possible. With this increase in sensitivity, there is the heightened risk of detecting cellular material unrelated to an alleged event and has been inadvertently introduced into a sample through contamination. The implications of contaminations vary, however these events have the potential to have serious consequences. For this reason, it is essential that best practice in contamination minimisation procedures are used throughout all stages of the handling and processing of forensic evidence.
Forensic laboratories apply rigorous Quality Assurance programs to minimise and detect contamination. Forensic staff contamination can usually be detected through the comparison of all DNA profiles produced within a laboratory to an elimination database that contains the DNA profiles of individuals who are involved in the processing of evidentiary items. The ability to detect contamination by identifying DNA matches with samples from forensic staff through comparison to a laboratory elimination database is limited to the individuals present on the database and does not indicate how and when the transfer occurred. While measures exist to detect contamination by forensic staff, sample-to-sample contamination is more difficult to identify and is therefore more likely to go undetected.
To understand the potential risk for exhibit contamination, it is important to understand the transfer and persistence of DNA, especially within areas where forensic exhibits and samples are processed. It is also essential to identify items which are efficient DNA transfer vectors, and any processes that may facilitate these inadvertent transfer events. Previous research indicates that exhibit packaging can act as an efficient vector for DNA transfer, however before this project, the extent of this transfer, and the contamination risk posed to exhibits, was largely unknown. An overview of previous research which relates to DNA transfer within forensic laboratories and involves exhibit packaging has been provided within Chapter 1.
Within the next chapter (Chapter 2), the levels of DNA which accumulate on the packaging of casework exhibits during routine forensic processing, and specifically throughout the exhibit examination process, was examined. In addition, the source of the accumulating DNA was investigated. Observation of the potential for DNA from an exhibit to accumulate on the exterior of its packaging raised the question of the potential for DNA from the exhibit to be transferred further. This concept was explored within Chapter 3, which investigated the DNA accumulating within forensic workspaces within exhibit storage locations. The question of the potential mechanism involved in the accumulation of exhibit DNA on packaging and the successive transfer of this DNA was addressed within Chapter 4, where DNA transfer between and through the porous surface of paper evidence bags was examined.
This research assists with filling an important knowledge gap within the existing DNA transfer and persistence literature and provides the forensic community with an understanding of the level of exhibit contamination risk posed by DNA that accumulates on exhibit packaging. The data presented within this work demonstrates the potential for exhibit packaging to act as an efficient DNA transfer vector and reinforces the need for police and forensic laboratories to review their current contamination minimisation procedures, to ensure that they are adequate, given the highly sensitive modern DNA profiling technologies.
Keywords: DNA Transfer, Trace DNA, Exhibit, Exhibit storage, Exhibit packaging, DNA contamination, STR DNA profiling
Subject: Forensic & Analytical Chemistry thesis
Thesis type: Doctor of Philosophy
Completed: 2025
School: College of Science and Engineering
Supervisor: Adrian Linacre