A sexual assault evidence collection kit contains tools to collect evidence from a victim of sexual assault; the collection is performed by a medical professional, usually a specially trained nurse (Sexual Assault Nurse Examiner). The contents of a kit generally include swabs, blood collection tubes, microscope slides, a comb, and evidence collection envelopes for hairs and fibers. The victim is swabbed for any biological evidence that may contain the perpetrator’s DNA (e.g., skin, saliva, or semen).
The evidence in the kit can then be sent to a crime laboratory, alongside other crime scene evidence such as clothing, bed sheets, toxicology reports, or weapons. The laboratory will analyze the collective suite of evidence for traces of semen, saliva, or other body fluids; such analysis is performed via chemical and blood (serology) tests, as well as examination of microscope slides for the presence of sperm.
Evidence from the sexual assault kit found to have semen or other biological fluids can be kept for DNA analysis. DNA is the molecule containing our genetic code. DNA testing involves isolating DNA from a biological sample (e.g., blood, saliva) and creating a DNA profile (also known as a DNA “fingerprint”) that is a unique identifier of an individual. The sexual assault victim’s DNA will also be profiled to isolate her/his DNA from any other person’s DNA found on the evidence. If there is a suspect in the case, any foreign DNA profile will be compared to the DNA profile of the suspect. For cases without a suspect, any foreign DNA profile(s) will then be compared with DNA profiles in databases such as the Combined DNA Index System (CODIS).
A research report by the DoJ’s National Institute of Justice demonstrates the utility of collecting and analyzing forensic evidence. For cases with evidence to link a suspect to a crime scene or victim, the report states “the conviction rate for [such cases] was significantly higher than cases without such evidence.”