Collection of Biological Evidence from Plastic Using Various Types of Swabs
Henderson, Samantha Kim
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DNA can be left behind at a crime scene when a person comes in contact with a surface. However, not all DNA samples will result in a DNA profile because the amount of DNA recovered from the sample may not be adequate. Any increase in the yield of DNA recovered from crime scene samples improves the chances of producing probative DNA profiles for court. DNA results presented in court can be used to help determine a suspect's guilt or innocence.Because of DNA's attraction to the silica in glass-fiber material, an increased adsorption of DNA to glass-fiber swabs may improve the collection and recovery of DNA from plastic evidence. The efficiency of glass-fiber swabs compared to polyester-tipped and cotton-tipped swabs for recovering DNA from plastic remained unknown. Since many common items are now made from plastic, further study was needed in order to determine which swab type was more effective for recovering DNA from plastic evidence.This study was designed to compare glass-fiber swabs with polyester-tipped and cotton-tipped swabs to determine if glass-fiber swabs would improve the recovery of DNA from plastic evidence. Human blood was spotted on and collected from a plastic Rubbermaid® lid. DNA was isolated from the collection swabs, amplified by polymerase chain reaction, and quantified with the Q-TAT multiplex assay. The quantity of DNA recovered by the different types of swabs was then compared.Glass-fiber swabs, polyester-tipped swabs, and cotton-tipped swabs do differ in their respective effectiveness for recovering DNA from blood stains spotted and dried onto a plastic Rubbermaid® lid. In the final analysis, cotton-tipped swabs were more effective than glass-fiber swabs and polyester-tipped swabs for recovering DNA from plastic. Further study showed that cotton-tipped swabs recovered more DNA from glass than polyester-tipped swabs and were equal, compared to polyester-tipped swabs, in recovering DNA from tile and wood.
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