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  • Experimental studies offer a means

    2019-10-08

    Experimental studies offer a means of developing an empirical basis for the development of forensic protocols in the investigations of specific crime types [12]. Such an evidence NESS 0327 for ICST cases will help enable the identification of situations when there is likely to be recoverable DNA from an item of clothing, and the extent to which a viable profile may be produced. Understanding the ‘evidence dynamics’ of this form of trace evidence within the context of ICST offences will, therefore, provide valuable insight into the best use of the often limited resources during the course of an investigation. Studies into the UK ICST cases indicated that victims were often picked up while on their way to or from school [1], [3] and as such, items of clothing that constitute elements of a school uniform in the UK (T-shirt, trousers, tights) were examined in this study. These items of clothing were stained with semen and then stored at the back of a wardrobe for eight months before being laundered. This process simulated how an ICST victim is known to have treated the clothing they were wearing when the sexual offence(s) took place. Given the more common incidence of multiple offenders and the potential for multiple washing of clothing to have occurred before a victim is identified in ICST cases, the persistence of DNA in semen stains on items laundered once, twice and three times, and in laundered semen stains from multiple donors were investigated.
    Materials and methods
    Results
    Discussion The results from this study demonstrate for the first time that profilable DNA can be recovered from laundered semen stains after an eight-month lag time between semen deposition and laundering, as is often seen in ICST cases. The results also demonstrate that profilable DNA can be obtained from semen-stained clothing that has been laundered multiple times, and confirm the findings of previous research [6], [8], [9], [10] that DNA profiles can be obtained from semen-stained clothing laundered just once. High quantities of DNA, in the microgram rather than nanogram range, were recovered from the laundered semen stains. These were significantly higher than the quantities of DNA of approximately 0.6–7.5ng previously recovered from semen-stained underwear (calculated from the concentrations and elution volume reported by Farmen et al. [7]). This difference in the quantities of DNA between the present study and the study of Farmen et al. [7] could be due to differences in the wash programmes used (e.g. the temperature setting and type of detergent used), given that similar initial semen deposits and materials were used (0.5cm2 samples of 1ml semen stains versus 1cm2 samples of 0.5ml semen stains). It is also hypothesised that the long lag period in the present study, as opposed to just 24h between semen deposition and laundering in the study by Farmen et al. [7], could have made the stains more resistant to the washing process. It is also possible that, as different donors were used in these two studies (one donor in this study, and 5 donor mixture in the Farmen et al. [7] study), a variation in sperm count may account for a difference in the amount of recoverable DNA. Similarly high quantities of DNA were recovered from the laundered semen stains, regardless of wash temperature, detergent used, material type, or number of washes, although very varied results were obtained (Fig. 1, Fig. 2). Wash conditions and type of material have previously been found to have varying degrees of influence on DNA recovered from laundered semen stains. For example, Nussbaumer et al. [10] reported that the highest amounts of DNA from laundered semen stains were found after washing at 60°C, whereas Farmen et al. [7] concluded that twice the amount of DNA was recovered from semen stains laundered at 40°C than at 60°C. Transfer of DNA among items of clothing within the washing machine may have also affected the amounts of DNA NESS 0327 recovered.