Gunshot residue (GSR): Frequency of residue types encountered in case work and background levels on control samples.

The evaluation of criminal cases involving the discharge of a firearm requires reliable and up to date information regarding the transfer and persistence of gunshot residue (GSR). Similarly, knowledge of background levels of GSR on relevant populations and awareness of the potential for contamination/secondary transfer is essential. In this paper we build on previous work published by this laboratory and provide an update on the frequency of gunshot residue types in discharged cartridge casings (DCC) encountered in casework within the Republic of Ireland. In conjunction, an examination of the types of firearms encountered in casework and the associated residue types is undertaken. Finally, a review of levels of GSR particles detected on control samples taken from members of An Garda Síochána, the Irish police is detailed. Control samples are taken before a police officer samples a detainee suspected of involvement in an incident where a firearm was discharged and/or subsequently handled.

The transfer of touch DNA from hands to glass, fabric and wood.

The transfer of DNA from hands to objects by holding or touching has been examined in the past. The main purpose of this study was to examine the variation in the amount of DNA transferred from hands to glass, fabric and wood. The study involved 300 volunteers (100 for glass, 100 for fabric and 100 for wood) 50% of which were male and 50% female. The volunteers held the material for 60s. The DNA was recovered from the objects using a minitape lift, quantified using the Quantifiler kit assay, extracted using a 'Qiagen(®) QIAamp DNA mini kit' and amplified using the AmpFlSTR(®) SGM Plus™ Amplification Kit at 28 cycles. The results show that using ANOVA there was a significant difference (F=8.2, p<0.05) between the three object types in the amount of DNA recovered. In terms of DNA transfer and recovery, wood gave the best yield, followed by fabric and then glass. The likelihood of success of obtaining a profile indicative of the holder was approximately 9% for glass samples, 23% for fabric and 36% for wood. There was no significant difference between the amount of DNA transferred by male or female volunteers. In this study good shedder status, as defined by obtaining useful profiles of 6 or more alleles, is estimated at approximately 22% of the population. The phenomenon of secondary transfer was observed when mixed DNA profiles were obtained but the incidence was low at approximately 10% of the total number of samples. DNA profiles corresponding to more than one person were found on objects which had been touched by only one volunteer. Although secondary transfer is possible the profiles obtained from touched objects are more likely to be as a result of primary transfer rather than a secondary source.

Distinguishing between damage to clothing as a result of normal wear and tear or as a result of deliberate damage: a sexual assault case study.

This paper focuses on bra damage, specifically damage observed in hook and eye fasteners that are generally located at the backstraps of bras. We describe bra design including the method by which hook and eye fasteners are generally constructed. We assess bra damage in two situations where the damage observed was unexpected given the case scenarios. These were: (i) the complainant of an alleged rape attributed damage to her bra hooks to force during a struggle and (ii) the complainant had earlier manipulated her bra hooks in an incident not related to her complaint. Steriomicroscopy and reconstruction experimentation were necessarily used to assess the bra damage. A systematic approach to damage analysis was employed by the forensic practitioners to correctly identify damage as being a result of mechanical manipulation and therefore as falsified. This paper suggests that more examples of falsified damage should be documented.