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Isolation and Identification of Female DNA on Postcoital Penile Swabs

Cina, Stephen J. M.D., MAJ, USAF, MC, FS; Collins, Kim A. M.D.; Pettenati, Mark J. Ph.D.; Fitts, Matthew Ph.D.

American Journal of Forensic Medicine & Pathology: June 2000 - Volume 21 - Issue 2 - pp 97-100
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After sexual assault, cells originating from the assailant may be recovered from the victim. Through polymerase chain reaction (PCR)-based technology, positive scientific identification of the assailant may be made from these cells. Described is a prospective study describing a method for positively identifying cells from a female sex partner obtained from postcoital swabs of the penis of the male sex partner. Swabs were taken from the penis of a man at 1- to 24-hour intervals after coitus. DNA was isolated from each swab through standard organic extraction methods. The presence of female DNA was detected using the gender-specific amelogenin marker. Extracted DNA was amplified for eight different genetic loci using the Promega PowerPlex kit (Promega) and Amplitaq Gold (Perkin Elmer). Amplified samples were electrophoresed on precast sequencing gels (Hitachi) and were analyzed fluorescently using Hitachi's FMBIO 2 fluorescent scanner and software. Each sample obtained from a penile swab or condom was compared to male and female buccal controls. Female DNA was isolated from all postcoital penile swabs as determined by exclusive amplification of the X-chromosome specific 212 base pair amelogenin marker. In all cases, scientific identification of the female DNA from the swabs was determined by coamplification of eight STR loci (Power-Plex) and was compared to female and male control profiles. Cells shed from a female victim during sexual intercourse can be retrieved from the penis of a male offender after sexual intercourse during a 1- to 24-hour postcoital interval. DNA can be extracted from these cells and can be used to scientifically identify the female sexual participant through PCR-based technology. It is suggested that penile swabs be taken from alleged perpetrators of sexual assaults to associate them with a female victim.

From the Office of the Armed Forces Medical Examiner, 59th MDW/MTLP, Department of Pathology, Wilford Hall Medical Center, Lackland AFB, Texas (S.J.C.); Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina (K.A.C.); Department of Pediatrics, Cytogenetics Laboratory, Wake Forest University School of Medicine, Wake Forest, North Carolina (M.J.P.); and Forensic DNA/Serology, SC Law Enforcement Division, Columbia, South Carolina (M.F.).

Manuscript received May 12, 1999; revised July 29, 1999; accepted August 25, 1999.

This work was supported in part by Federal Formula grant 98-DB-MU-0045 awarded by the Bureau of Justice Assistance, U.S. Department of Justice through the South Carolina Department of Public Safety. The Assistant Attorney General, Office of Justice Programs, coordinates the activities of the following program offices and bureaus: Bureau of Justice Assistance, Bureau of Justice Statistics, National Institute of Justice, Office of Juvenile Justice and Delinquency Prevention, and the Office for Victims of Crime.

Points of view or opinions contained within this document are those of this author and do not necessarily represent the official position or policy of the U.S. Department of Justice, the Department of the Defense, or the United States Air Force. One author (S.J.C.) is a full-time federal employee and this work is in the public domain.

Address correspondence and reprint requests to Stephen J. Cina, Office of the Armed Forces Medical Examiner, 59th MDW/MTLP, Department of Pathology, Wilford Hall Medical Center, Lackland AFB, TX 78236, U.S.A.

© 2000 Lippincott Williams & Wilkins, Inc.