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Effects of Toluidine Blue and Destaining Reagents Used in Sexual Assault Examinations on the Ability to Obtain DNA Profiles From Postcoital Vaginal Swabs

NCJ Number
168693
Journal
Journal of Forensic Sciences Volume: 42 Issue: 2 Dated: (March 1997) Pages: 316-319
Author(s)
M N Hochmeister; M Whelan; U V Borer; C Gehrig; S Binda; A Berzlanovich; E Rauch; R Dirnhofer
Date Published
1997
Length
4 pages
Annotation
Toluidine blue is an important tool for detecting and documenting genital and perianal injuries following sexual assault.
Abstract
Application of toluidine blue dye and its subsequent removal from unstained areas by means of a destaining reagent, such as diluted acetic acid or a lubricant has been shown to increase the detection rate of posterior fourchette lacerations from 16 percent to 40 percent in adult rape victims. Currently, limited information on toluidine blue positive findings in sexually active control groups imposes some limitation on the interpretation of these injuries. Because injuries could otherwise be attributed to improper handling of an examination speculum or the improper insertion of the examining finger, the toluidine blue test should be performed prior to any digital or speculum examination and thus prior to the collection of forensic evidence. For forensic DNA identity testing, it becomes pertinent to determine whether toluidine blue and the destaining reagents used in a sexual assault examination have an adverse effect on the recovery of high-molecular-weight DNA from postcoital vaginal swabs and thereby have an impact on restriction fragment length polymorphism (RFLP) analysis or PCR-based tests. It is known that some of the lubricants used can have a destructive effect on sperm motility. In order to investigate the potential effects, postcoital vaginal swabs were taken 6 hours after sexual intercourse and exposed directly to 1 percent toluidine blue in aqueous solution, 1 to 10 percent acetic acid, and various surgical and vaginal lubricants. Subsequently, the DNA was isolated, and DNA identity typing was performed. The results show that these reagents have no negative effect on the obtaining of DNA profiles from shallow and deep vaginal swabs. 2 figures and 30 references