title: The Persistence of Sperm and the Development of Time Since Intercourse (TSI) Guidelines in Sexual Assault Cases at Forensic Science Ireland, Dublin, Ireland.
abstract: The persistence of sperm using confirmatory microscopic analysis, the persistence of sperm with tails, time since intercourse (TSI) analysis, and results from the acid phosphatase (AP) reaction from approximately 5581 swabs taken from circa 1450 sexual assault cases are presented. The observed proportions of sperm in the vagina and anus declines significantly after 48 h TSI, and sperm on oral swabs were observed up to 15 h TSI. The AP reaction as a predictor of sperm on intimate swabs is questioned. All AP reaction times gave a low true positive rate; 23% of sperm-positive swabs gave a negative AP reaction time. We show the AP reaction is an unsafe and an unreliable predictor of sperm on intimate swabs. We propose that TSI not AP informs precase assessment and the evaluative approach for sexual assault cases. To help inform an evaluative approach, TSI guidelines are presented.
authors.affiliation: Department of Justice and Equality, Forensic Science Ireland, Garda Headquarters, Phoenix Park, Dublin 8, Ireland.
authors.forename: David G
authors.initials: DG
authors.lastname: Casey
authors.affiliation: Department of Mathematics and Statistics, Maynooth University, Co. Kildare, Ireland.
authors.forename: Katarina
authors.initials: K
authors.lastname: Domijan
authors.affiliation: Department of Justice and Equality, Forensic Science Ireland, Garda Headquarters, Phoenix Park, Dublin 8, Ireland.
authors.forename: Sarah
authors.initials: S
authors.lastname: MacNeill
authors.affiliation: Department of Justice and Equality, Forensic Science Ireland, Garda Headquarters, Phoenix Park, Dublin 8, Ireland.
authors.forename: Damien
authors.initials: D
authors.lastname: Rizet
authors.affiliation: Department of Justice and Equality, Forensic Science Ireland, Garda Headquarters, Phoenix Park, Dublin 8, Ireland.
authors.forename: Declan
authors.initials: D
authors.lastname: O'Connell
authors.affiliation: Department of Justice and Equality, Forensic Science Ireland, Garda Headquarters, Phoenix Park, Dublin 8, Ireland.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ryan
mesh_terms: D000135:Acid Phosphatase / Q000032:analysis; D001003:Anal Canal / Q000166:cytology; D005260:Female; D005554:Forensic Medicine / Q000592:standards*; D017408:Guidelines as Topic; D006801:Humans; D007494:Ireland; D008297:Male; D008853:Microscopy; D009055:Mouth / Q000166:cytology; D012742:Sex Offenses; D013048:Specimen Handling; D013094:Spermatozoa / Q000737:chemistry / Q000166:cytology*; D013997:Time Factors; D014621:Vagina / Q000166:cytology
chemical_list: D000135:Acid Phosphatase
keywords: acid phosphatase; expert evaluative opinion; forensic science; persistence of sperm; sexual assaults; time since intercourse