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Abstract

As the capabilities of forensic science have advanced, so have the opportunities to recover forensic evidence to support a criminal investigation. An area where this has been most prominent is within DNA analysis with increasing sensitivities allowing interpretable DNA profiles to be obtained from minute traces of DNA left at a crime scene. As a result, the need to understand how DNA transfers and persists under varying conditions has increased, in order to maximise opportunities for DNA recovery and maintain the validity of interpretations. Sexual assault investigations remain one of the most complex crimes to investigate, as delayed reporting is common, and can lead to a lack of evidence available for analysis. Intimate swabs are routinely used in forensic examinations to collect DNA from the victim, however, collection is limited up to 7 days after the offence due to the continued degradation of DNA after initial deposition. Therefore, in cases where intimate swabs are no longer appropriate, clothing worn by the victim during an offence can be targeted for DNA analysis. The current research sought to identify the extent to which spermatozoa and associated DNA would persist on cotton underwear laundered repeatedly at 30ºC and 60ºC and the effect that detergent type would have on persistence. Additionally, this study aimed to establish if a routinely used differential lysis would impact spermatozoa or DNA yield on laundered samples. The findings demonstrate that spermatozoa and DNA can persist on cotton laundered up to five times, regardless of laundering condition however the extent of which varied. Furthermore, conducting a differential lysis can increase spermatozoa yields from mixed samples, however, may be destructive if applied to degraded or LCN samples. Overall, these findings suggest that clothing with suspected semen staining as a result of a sexual offence should be submitted for DNA analysis despite repeated laundering, even if a positive presumptive or confirmatory test result is not retrieved

Course: Criminal Justice - MSc - C2681F

Date Deposited: 2023-05-11

URI/permalink: https://library.port.ac.uk/dissert/dis14147.html