Semen is one of the most common biological fluids encountered by a forensic serologist on varying substrate types. Seminal fluid contains many enzymes, proteins, and cellular material such as acid phosphatase (AP), prostate-specific antigen (PSA), semenogelin (Sg), and spermatozoa; detection of these components can aid in the forensic identification of body fluids. Forensic laboratories usually follow a prescribed testing workflow (from visual examination including an alternate light source (ALS) and AP testing to PSA or Sg testing followed by a microscopic examination for sperm cells) to ensure laboratory resources are being used in a proper manner with minimal waste of both time and resources. However, this approach can be problematic when degradation of semen stains results in the inability to detect the presence of certain seminal components. When a stain yields negative results for an AP reaction, no further analyses for semen may be performed and analysis comes to an end. In common practice, evidentiary items containing biological fluids may not be immediately recovered following an incident and/or may not be stored properly, causing contamination or exposure of these biological fluids to harsh environments, potentially degrading the sample. This study investigates how exposure to different environmental conditions and packaging types affects the degradation of the four most common semen components targeted in forensic testing: AP, PSA, Sg, and spermatozoa.
Semen stains were prepared and exposed to ten different storage and/or environmental conditions to compare their effects on the detectability of seminal components (fluorescence, AP, PSA, Sg, and spermatozoa as well as deoxyribonucleic acid (DNA) testing) for a period of approximately four months. Samples from each condition were tested on select days throughout the study. Minimal changes in detection of the seminal components were observed under the five conditions in which the stains remained dry: packaged in paper stored at room temperature, packaged in paper stored at high temperatures, exposed to sunlight, exposed to ultraviolet light, and stored in high humidity. Two of the conditions involved exposure to outdoor environments. The stains openly exposed to the elements or buried in soil exhibited the most notable degradation of all components when compared to other conditions. Negative results were obtained for nearly all seminal components (AP, PSA, or Sg) on Day 8 for stains openly exposed outdoors and Day 32 for buried samples. The remaining three conditions exposed the stains to damp or wet conditions and gave variable results throughout the study.
DNA quantification was performed for select samples from each condition to assess DNA degradation. Most samples did not exhibit DNA degradation on quantification results up to Day 112; however, two samples exposed to outdoor environments exhibited DNA degradation as early as Day 8 (earliest day quantified). More notably, two samples from Day 112 demonstrated the presence of non-degraded DNA in sufficient quantity for profiling, while the presumptive semen analyses (AP, PSA, and Sg) for the same samples exhibited negative results when using an AP reaction cut-off time of 2 minutes. These results suggest that an allotted time of 2 minutes for AP detection may not be sufficient in some samples, and that valuable DNA evidence may go undiscovered, especially when other presumptive tests show negative results.
Overall, the results revealed variation in the sequence and rate of degradation for seminal components in semen stains exposed to different environmental conditions. It was not possible to predict which of the remaining components of semen would be detectable based on the outcome of any one of the tests. Therefore, it is recommended that comprehensive testing of possible semen stains is performed, even after negative presumptive results are obtained, when the case scenario suggests exposure to damp/wet or otherwise less than ideal conditions.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/43742 |
| Date | 31 January 2022 |
| Creators | Twanabasu, Bishakha |
| Contributors | Brodeur, Amy N. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution-NonCommercial 4.0 International, http://creativecommons.org/licenses/by-nc/4.0/ |
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