ISSN: 0022-1198
CODEN: JFSCA
Page Count: 4

Effects of Toluidine Blue and Destaining Reagents Used in Sexual Assault Examinations on the Ability to Obtain DNA Profiles from Postcoital Vaginal Swabs
Berzlanovich, A
Medical examiner, Institute of Legal Medicine, University of Vienna,

Gehrig, C
Research scientists, and director, Institute of Legal Medicine, University of Berne,

Rauch, E
Medical examiner, Institute of Legal Medicine, University of Munich,

Hochmeister, MN
Research scientists, and director, Institute of Legal Medicine, University of Berne,

Whelan, M
Forensic nurse examiner, Pomerado Hospital, CA

Dirnhofer, R
Research scientists, and director, Institute of Legal Medicine, University of Berne,

Binda, S
Research scientists, and director, Institute of Legal Medicine, University of Berne,

Borer, UV
Research scientists, and director, Institute of Legal Medicine, University of Berne,

(Received 4 June 1996; accepted 2 August 1996)

Abstract

Toluidine blue is an important tool to detect and document genital and perianal injuries following sexual assault. 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% to 40% 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 h after sexual intercourse and exposed directly to 1% toluidine blue in aqueous solution, 1–10% acetic acid, and various surgical and vaginal lubricants. Subsequently, the DNA was isolated and DNA identity typing (RFLP and PCR-based) was performed. The results demonstrate, that these reagents have no negative effect on the ability to obtain DNA profiles, either RFLP or PCR-based, from shallow and deep vaginal swabs. The quantity and quality of extractable high molecular weight DNA obtained was comparable with that from uncontaminated postcoital vaginal swabs. RFLP patterns and PCR-based typing results on the D1S80, HUMTH01, TPOX, and CSF1PO loci were consistent with the uncontaminated control swabs and the corresponding whole blood samples of the donors. Therefore, evidentiary material inadvertently contaminated with these reagents can be successfully typed.

Keywords:
forensic science, sexual assault, vaginal swabs, perineal lacerations, toluidine blue, acetic acid, lubricants, DNA, restriction fragment length polymorphism, polymerase chain reaction, genetic typing, D2S44, D4S139, D5S110, D10S28, TH01, TPOX, CSF1PO

Paper ID: JFS14119J
DOI: 10.1520/JFS14119J
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