Collection of physical evidence

Physical evidence is anything tangible that can establish that a certain crime was committed or linking the evidence with the crime and victim. Collection of physical evidence requires an investigator to first recognize that evidence. some of the physical evidences may include the pieces of cloths worn during the scene, beddings, or inform of semen, blood, hairs, and skin fibers.

The victim should preserve the beddings or any other object on which the rape took place and take it to the crime lab for analysis. The contact between the victim and the preparator may have resulted in the transfer of physical evidence in the form semen, blood and hairs. This will prove vital in identifying the assailant and prosecuting the case.

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.