Thesis
Early-stage investigation into potential degradative effects of varied soils on human semen for the purpose of forensic investigation
Masters by Research, Murdoch University
2023
Abstract
The ability to identify and link an individual to a victim, crime scene, or offender is one of the pillars of forensic science. DNA evidence has become the gold standard in analytical techniques, leading to higher accuracy in human identification than other methods. Semen is a common vehicle for unknown DNA within a crime scene and provides additional sexual context to the crime in question. However, when found outdoors, semen can be contaminated with soil, potentially leading to a reduction in evidence quality. To this end, the following pilot study investigating the effects of soil on DNA within semen has been produced. Semen collected from three confirmed spermatic individuals was exposed to four different soils and one control substrate (4 grams sterile bricklayers’ sand, bleached sand, bentonite clay, Southwest Australian native soil mix; non-porous polystyrene as the control surface) in 10μl allotments and remained on the test surface for 1 to 96 hours at a constant temperature (19°C - 21°C) away from light and additional moisture. Genetic integrity was assessed via the comparison of autosomal targets to form a degradation index as well as quantification of multiple small autosomal amplicons; degradation was analysed in tandem with genetic profile completeness through the use of the multiplex STR human identification PowerPlex® 21. Analysis showed that there was no significant difference in the quantity, quality, or direct forensic applicability between four of the five substrates tested, with results from bentonite clay likely being due to lack of accessible DNA, not degradation. Results also show that changes in soil pH, porosity, hydrophobicity, and foreign bacterial presence did not directly affect the degradation of DNA found within the tested human sperm. By comparing these results to previous and future studies within the forensic research space, the exact variables that influence DNA degradation for semen samples found in these contexts will be revealed.
Details
- Title
- Early-stage investigation into potential degradative effects of varied soils on human semen for the purpose of forensic investigation
- Authors/Creators
- Lee C Barbour
- Contributors
- Shane Tobe (Supervisor) - Murdoch University, Centre for Biosecurity and One HealthGarth Maker (Supervisor) - Murdoch University, Centre for Computational and Systems MedicineFiona Baxter (Supervisor)
- Awarding Institution
- Murdoch University; Masters by Research
- Identifiers
- 991005612268407891
- Murdoch Affiliation
- School of Medical, Molecular and Forensic Sciences
- Resource Type
- Thesis
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