Rape investigation

Rape investigation is the procedure to gather facts about a suspected rape, including forensic identification of a perpetrator, type of rape and other details.

The vast majority of rapes are committed by persons known to the victim: only five percent of assaults are perpetrated by a stranger according to one survey. Therefore, the identity of the perpetrator is frequently reported. Biological evidence such as semen, blood, vaginal secretions, saliva, vaginal epithelial cells may be identified and genetically typed by a crime lab. The information derived from the analysis can often help determine whether sexual contact occurred, provide information regarding the circumstances of the incident, and be compared to reference samples collected from patients and suspects. Medical personnel in the United States of America collect evidence for potential rape cases by using rape kits.

DNA profiling is used by crime laboratories for testing biological evidence, most commonly by means of the polymerase chain reaction (PCR), which allows analysis of samples of limited quality and quantity by making millions of copies. An advanced form of PCR testing called short tandem repeats (STR) generates a DNA profile that can be compared to DNA from a suspect or a crime scene. Blood, buccal (inner cheek) swabbings or saliva should also be collected from victims to distinguish their DNA from that of suspects.

Criminals may plant fake DNA samples at crime scenes. In one case Dr. John Schneeberger, who raped one of his sedated patients and left semen on her underwear, surgically inserted a Penrose drain into his arm and filled it with foreign blood and anticoagulants. Police drew what they believed to be Schneeberger's blood and compared DNA on three occasions without a match.

...
Wikipedia