title: Isolating DNA from sexual assault cases: a comparison of standard methods with a nuclease-based approach.
abstract: BACKGROUND
  Profiling sperm DNA present on vaginal swabs taken from rape victims often contributes to identifying and incarcerating rapists. Large amounts of the victim's epithelial cells contaminate the sperm present on swabs, however, and complicate this process. The standard method for obtaining relatively pure sperm DNA from a vaginal swab is to digest the epithelial cells with Proteinase K in order to solubilize the victim's DNA, and to then physically separate the soluble DNA from the intact sperm by pelleting the sperm, removing the victim's fraction, and repeatedly washing the sperm pellet. An alternative approach that does not require washing steps is to digest with Proteinase K, pellet the sperm, remove the victim's fraction, and then digest the residual victim's DNA with a nuclease.
  
  
  METHODS
  The nuclease approach has been commercialized in a product, the Erase Sperm Isolation Kit (PTC Labs, Columbia, MO, USA), and five crime laboratories have tested it on semen-spiked female buccal swabs in a direct comparison with their standard methods. Comparisons have also been performed on timed post-coital vaginal swabs and evidence collected from sexual assault cases.
  
  
  RESULTS
  For the semen-spiked buccal swabs, Erase outperformed the standard methods in all five laboratories and in most cases was able to provide a clean male profile from buccal swabs spiked with only 1,500 sperm. The vaginal swabs taken after consensual sex and the evidence collected from rape victims showed a similar pattern of Erase providing superior profiles.
  
  
  CONCLUSIONS
  In all samples tested, STR profiles of the male DNA fractions obtained with Erase were as good as or better than those obtained using the standard methods.
authors.affiliation: Confarma France SARL, Zone Industrielle Canal d'Alsace, Hombourg, 68490, France. alex.garvin@uha.fr.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Garvin
authors.forename: Andrea
authors.initials: A
authors.lastname: Fischer
authors.forename: Jutta
authors.initials: J
authors.lastname: Schnee-Griese
authors.forename: Andrea
authors.initials: A
authors.lastname: Jelinski
authors.forename: Michel
authors.initials: M
authors.lastname: Bottinelli
authors.forename: Gianni
authors.initials: G
authors.lastname: Soldati
authors.forename: Monica
authors.initials: M
authors.lastname: Tubio
authors.forename: Vincent
authors.initials: V
authors.lastname: Castella
authors.forename: Nathalie
authors.initials: N
authors.lastname: Monney
authors.forename: Naseem
authors.initials: N
authors.lastname: Malik
authors.forename: Michelle
authors.initials: M
authors.lastname: Madrid