Rape investigation
Encyclopedia
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 two 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.
(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 repeat
s (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 anticoagulant
s. Police drew what they believed to be Schneeberger's blood and compared DNA on three occasions without a match.
Recent coitus can be determined by performing a vaginal wet-mount microscopy examination (or oral/anal if indicated) for detection of motile sperm, which are seen on the slide if less than three hours have elapsed since ejaculation. However only one-third of sexual assaults result in ejaculation into a body orifice. Further, the alleged assailant may have had a vasectomy or have experienced sexual dysfunction (roughly 50 percent of assailants suffer from impotence or ejaculatory dysfunction). In addition, acid phosphatase
levels in high concentrations is a good indicator of recent coitus. Acid phosphatase is found in prostatic secretions and activity decreases with time and is usually absent after 24 hours. Prostate-specific antigen (PSA
) may be detected within a 48-hour period. The seminal fluid of vasectomized men also contains a significant PSA level. Nonmotile sperm may be detected even beyond 72 hours after intercourse depending on staining techniques.
Rape
Rape is a type of sexual assault usually involving sexual intercourse, which is initiated by one or more persons against another person without that person's consent. The act may be carried out by physical force, coercion, abuse of authority or with a person who is incapable of valid consent. The...
, including forensic identification
Forensic identification
Forensic identification is the application of forensic science, or "forensics", and technology to identify specific objects from the trace evidence they leave, often at a crime scene or the scene of an accident. Forensic means "for the courts"....
of a perpetrator, type of rape
Types of rape
Rape can be categorized in different ways: for example, by reference to the situation in which it occurs, by the identity or characteristics of the victim, and/or by the identity or characteristics of the perpetrator...
and other details.
The vast majority of rapes are committed by persons known to the victim: only two 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
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...
, blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
, vaginal secretions, saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
, vaginal epithelial cells may be identified and genetically typed by a crime lab
Crime Lab
A crime laboratory - often shortened to crime lab - is a scientific laboratory, using primarily forensic science for the purpose of examining evidence from criminal cases.- Lab personnel :A typical crime lab has two sets of personnel:...
. 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
DNA profiling is used by crime laboratories for testing biological evidence, most commonly by means of the polymerase chain reactionPolymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
(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 repeat
Short tandem repeat
A short tandem repeat in DNA occurs when a pattern of two or more nucleotides are repeated and the repeated sequences are directly adjacent to each other. The pattern can range in length from 2 to 5 base pairs and is typically in the non-coding intron region...
s (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
John Schneeberger
John Schneeberger is a South African former physician who lived and practiced in Canada, who drugged and raped one of his female patients and his stepdaughter...
, who raped one of his sedated patients and left semen on her underwear, surgically inserted a Penrose drain
Penrose drain
A Penrose drain is a surgical device placed in a wound to drain fluid. It consists of a soft rubber tube placed in a wound area, to prevent the build up of fluid.It is named for the American gynecologist Charles Bingham Penrose -Common uses:...
into his arm and filled it with foreign blood and anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...
s. Police drew what they believed to be Schneeberger's blood and compared DNA on three occasions without a match.
Circumstances and type of rape
Abrasions, bruises and lacerations on the victim help elucidate how a rape was carried out. 8 to 45 percent of victims show evidence of external trauma, most commonly at the mouth, throat, wrists, arms, breasts and thighs: trauma to these sites comprise approximately two thirds of injuries, while trauma to the vagina and perineum account for approximately 20 percent.Recent coitus can be determined by performing a vaginal wet-mount microscopy examination (or oral/anal if indicated) for detection of motile sperm, which are seen on the slide if less than three hours have elapsed since ejaculation. However only one-third of sexual assaults result in ejaculation into a body orifice. Further, the alleged assailant may have had a vasectomy or have experienced sexual dysfunction (roughly 50 percent of assailants suffer from impotence or ejaculatory dysfunction). In addition, acid phosphatase
Acid phosphatase
Acid phosphatase is a phosphatase, a type of enzyme, used to free attached phosphate groups from other molecules during digestion. It is basically a phosphomonoesterase...
levels in high concentrations is a good indicator of recent coitus. Acid phosphatase is found in prostatic secretions and activity decreases with time and is usually absent after 24 hours. Prostate-specific antigen (PSA
PSA
PSA may refer to:* PSA International , world's second largest port operator* PSA Peugeot Citroën, French vehicle manufacturer...
) may be detected within a 48-hour period. The seminal fluid of vasectomized men also contains a significant PSA level. Nonmotile sperm may be detected even beyond 72 hours after intercourse depending on staining techniques.