Investigating rape crimes, Part 2: Evidence collection and analysis
In the June issue, the first installment of this series on investigating the crime of rape discussed legal definitions, the importance of care in handling the initial contact with a rape victim and the goals for searching the crime scene. I pointed out successful prosecution of the crime often hinges on associative evidence collaborating a rape occurred and linking a suspect to the scene and/or the victim. This second part focuses on the types of evidence investigators might collect and analyze at the crime scene and from the victim.
Evidence Identification & Collection
Although many departments employ specialized personnel to process crime scenes, all police officers should possess a thorough knowledge of their crime laboratory's forensic capabilities and understand the importance of securing and collecting evidence.
While there is no substitute for training and experience, the collection and preservation of crime-scene evidence is not just the purview of evidence technicians and detectives. Except in very complex cases, the average police officer is capable of reconstructing the scene of the crime and conducting a systematic search for evidence.
As I explained in my previous column, in a rape there are two crime scenes: the location where the rape took place and the rape victim's physical person, including the clothing worn by the victim and the perpetrator.
Studies indicate up to 80 percent of rapes occur indoors, and the majority of cases involve some type of relationship between the victim and perpetrator. Unless it's a stranger-to-stranger rape case, the perpetrator often claims intercourse was consensual, and without any associative evidence to the contrary, the victim's word is pitted against the perpetrator's claims. So, investigators should photograph and videotape any sign of a struggle at the scene, such as broken furniture or other objects and items in disarray. Further evidence of a struggle includes injury to the victim; these photographs are normally taken at the hospital.
Preserve the bedding, or any other object on which the rape took place, and send it to the crime lab for analysis. The contact between the victim and the perpetrator may have resulted in the transfer of physical evidence in the form of semen, blood, hairs, skin fibers or other trace evidence, which will prove vital in identifying the assailant and/or prosecuting the case.
Properly collect all such evidence, including the clothing and undergarments worn by the victim. Evidence technicians use oblique and ultraviolet light to help spot hair and fibers, and blue light to assist in detecting semen.
One discrepancy between books on forensic science and real-life investigations is the suggestion the victim should be asked to disrobe over a clean cloth or bed sheet so any fibers or loose pubic hairs from the perpetrator can be properly collected. In an ideal world, this would be the perfect way to collect this type of evidence.
However, only in the mind of the scientist or academician do rapes occur in a sterile environment conducive to this type of evidence collection. Although most rapes do occur inside, the crime scene may be the stairway of large apartment building, the bathroom of a bar or nightclub, the inside of a vehicle or some other location not conducive to this type of evidence gathering.
Whether the victim is suffering from shock, lying in a fetal ball or is otherwise injured from her attacker, our first responsibility is to provide the victim with medical attention at a hospital. Even if the victim were able to disrobe at the scene, this must be conducted by a female police officer. Since female officers make up only about 12 percent of police forces nationally, a female officer may not be readily available to provide this type of evidence collection.
In the majority of cases, a search of the victim's clothing for crime evidence is done at the hospital. This is often a better setting in which to ask the victim to disrobe, take photographs of any injuries to her body and place each article of clothing in a separate container for later lab analysis. The chain of custody of evidence is vital, so a police officer must accompany the victim to the hospital, meaning an officer must ride in the ambulance with the victim.
The Medical Examination
Big city or small town, the fact remains doctors are not usually in the business of evidence collection. Although rape victim collection kits are standard issue at almost every medical facility, this does not mean medical practitioners will collect evidence properly. Those in charge of the department's investigative function must take responsibility for ensuring the proper liaison exists between the department and the community's hospital(s). This means meeting with doctors and staff, and explaining the nuances of the necessity for evidence and the information it can provide (see "The Medical Examination: Collection of Physical Evidence"). Ahospital staff meeting is an opportune time for police and medical professionals to discuss not only how they will work together to handle rape cases, but also how they will preserve the chain of custody of evidence.
The associative evidence collected during the medical examination proves most useful in cases where the victim does not know the perpetrator. However, even if investigators know the victim's assailant and make an arrest shortly after the crime based on probable cause, it's still critical all evidence protocols described in this article be followed. Arrest only requires probable cause. Conviction in court requires a much higher standard: proof beyond a reasonable doubt. Experienced investigators know the variables under which an arrest is initially made can change for various reasons: the evidence does not support the initial claims of the victim or witnesses, people change their versions of what they initially say occurred, the perpetrator claims sex was consensual and so on. Our system of justice relies heavily on tangible evidence, because emotion or perception does not affect it and logical conclusions can be drawn from the science supporting what the evidence represents.
As I stated earlier, investigators must photograph any physical injury to the victim, such as bruises and bleeding. Biological evidence, such as semen, may indicate sexual intercourse did take place, but that does not establish a prima facie case of rape. Injury to the victim is corroborative evidence of violence and is especially useful in cases where the suspect claims consensual sex.
Deoxyribonucleic Acid (DNA)
The Combined DNA Index System (CODIS)
The next installment of this rape investigation series will bring together the concepts from the first two articles by discussing the investigation of the hypothetical case of Marie Delaney, a bank vice president who was raped and left for dead in a parking garage while returning to her car.
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