Special Considerations for Sexual Assault Evidence
George Schiro
Forensic Scientist
Louisiana State Police Crime Laboratory
When dealing with sexual assaults, the investigator usually has a living victim who can provide the investigator with information which will help in collecting and preserving the pertinent evidence. The investigator should glean as much information as possible, so he or she will know which evidence to collect. For example, if the victim tells the investigator (which in this case may be the examining physician) that no oral penetration occurred, then the investigator knows that no oral swabs will need to be taken. Any information should be passed on to the crime lab, so the forensic scientists will know how to process the evidence submitted. Evidence should never be submitted without communicating relevant information.
When dealing with sex crimes, the victim should be taken to the hospital immediately and the examination started as soon as possible. Photographs should be taken to document any injuries which the victim received. If necessary, oral, vaginal, and/or anal swabs should be taken from the victim and air dried for one hour in a moving air source as soon as possible. They should be collected as soon as possible because the body begins breaking down the various components in seminal fluid through drainage, enzyme activity, pH, etc. The swabs should be air dried under a fan for at least one hour. This can either be accomplished by the doctor at the hospital, or, upon collecting the kit from the doctor, the investigator should bring it immediately to a secure place and air dry it. The reason for this is that the moisture in the swabs allows microorganisms to grow which can destroy the evidentiary value of the swabs. Known saliva samples from the victim must also be air dried along with any other wet or moist samples (not including whole blood samples, vaginal washing or any other liquid samples collected).
Usually, the best sample of seminal fluid comes from the swabs, as long as they are preserved properly. The next best place is usually the victim's panties because the seminal fluid will drain into the panties (if the assault was vaginal or anal in nature). The stain will sometimes be better preserved because the seminal fluid tends to dry faster in the panties. If the panties have wet stains, then they should be air dried as soon as possible before packaging. Clothes can be a good source of seminal fluid if the assailant ejaculated on the victim's clothes. The clothes can also be a source for the suspect's blood, hairs, fibers, or other evidence transferred to the victim from the suspect. Clothing should be air dried before permanent packaging and each article of clothing should be packaged separately.
Bed sheets, comforters, spreads, etc. can also be a source of evidence from the suspect. The value of this type of evidence should be carefully considered by the investigator before collecting it. If the bed is a "high traffic" area, meaning that numerous people have had access to the bed and the bed sheets haven't been cleaned in a long time, then it won't have as much evidentiary value as a bed where only one person had access to it and the sheets have been cleaned recently. The investigator should use the side lighting technique to look for any loose trace evidence on the sheets which may be lost during handling and packaging. This evidence should be placed in a paper packet and then placed in an envelope. If the sheets have wet stains and these can be attributed to the rape, then the investigator should circle these stains and inform the crime lab that those are the relevant stains to be examined. The investigator should note that he or she circled the stains and as always, air dry the evidence before permanently packaging it. The investigator should neatly fold the sheets inward to prevent the loss of any other loose evidence. The sheets can then be packaged separately in paper bags, air dried if necessary, and submitted to the crime lab.
If a suspect is established in a rape case, then reference samples should be collected from the suspect for comparison. These samples should include: a whole blood sample in a red, yellow, or purple top "Vacutainer"; a saliva sample (air dried); 15-20 pulled head hairs; and 15-20 pulled pubic hairs. If the suspect is captured within 24 hours and it can be established which clothes and/or shoes he wore during the attack, then the items should be packaged separately and submitted to the crime lab. Sometimes trace evidence from the victim such as hairs, fibers, blood, etc. can be found on the suspect's clothing.
The key to proper collection, preservation, analysis, and overall usefulness of evidence is open and plentiful communication between investigators, forensic scientists, and prosecutors. This will make the most of the evidence which can make or break a case. This paper has presented general guidelines on the collection and preservation of evidence. The investigator should remember that each crime scene is different and each crime scene is a learning process. The investigator should also keep in mind that different crime labs may like their evidence collected in different manners. This is why the investigator should not hesitate to call his or her crime lab if he or has a question or a problem on the collection or preservation of evidence.
by George Schiro
Louisiana State Police Crime Laboratory
P. O. Box 66614
Baton Rouge, LA 70896
Article submitted by the Author