Evidence Collection and Preservation

Athough this bulletin is not intended as an instructional manual for DNA evidence collection, every victim service provider should be aware of important issues involved in the identification, collection, transportation, and storage of DNA evidence. These issues are as important for the victim service provider as they are for the crime scene technician, nurse examiner, or other medical personnel. If DNA evidence is not initially identified, it may not be collected, and if DNA evidence is not properly collected, it may become contaminated or degraded. If properly preserved, however, DNA from body fluid stains or bones can be tested after many years in older cases in which questions of identity remain unresolved or disputed. In many cases, these substances can be analyzed to reliably link criminals to crimes or clear them as suspects.

It is crucial that victims of sexual assault understand why they should not change clothes, shower, or wash any part of their body after the assault. Semen may be found on clothing, bedding, or in the victim's vaginal, rectal, or oral regions. Saliva, which contains valuable DNA, can be found on an area where the victim was licked or bitten. In addition, if the victim scratched the assailant, skin tissue that contains the assailant's DNA can be collected from beneath the victim's fingernails.

Although evidence technicians may be able to collect fingerprints and other valuable forensic evidence from the crime scene, evidence that may be inside or on a victim's body should only be collected by a physician or sexual assault nurse examiner. A medical examination ideally should be conducted within hours of the assault to treat injuries, test for sexually transmitted diseases, and collect forensic evidence. The doctor or nurse examiner will use a special kit that contains sterile cotton swabs to collect fluids from the vaginal cavity, mouth, or other parts of the victim's body that may have come in contact with the assailant. Fingernail scrapings and hair also may be collected as forensic evidence at this time. The victim's clothes, especially undergarments, that were worn during and/or after the assault should be collected for evidentiary purposes. In addition, the examiner will take a control standard from the victim in the form of blood or saliva and may collect a sample of the victim's head and pubic hair. Given the sensitive nature of DNA evidence, victim service providers should contact their crime laboratory personnel or evidence technicians when collection questions arise.

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Understanding DNA Evidence: A Guide for Victim Service Providers
April 2001