Reference Citation: An earlier version of this paper was published as Schiro G. Collection and Preservation of Evidence. In: Muth AS, editor. Forensic Medicine Sourcebook. Detroit: Omnigraphics, 1999; 45-59.




George Schiro, MS, F-ABC

E-mail: Gjschiro@cs.com

(337) 322-2724




            When dealing with sexual assaults, the investigator usually has a living victim who can provide the investigator with information that 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. When gathering this information, the investigator must be aware that the victim might not be forthcoming with all of the information due to post traumatic stress, embarrassment, intoxication, diminished capacity, etc. 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 the victim received. Follow up photographs should be taken every five days because bruising that is not readily apparent after the attack will become more visible five to fifteen days after the initial injuries. More extensive bite mark documentation can also be done immediately after the initial rape exam. If intoxicants (alcohol, GHB, chloral hydrate, sleeping pills, etc.) are suspected of being involved, then whole blood samples in gray top "Vacutainers" and a urine specimen must also be collected. If possible, the urine specimen should be collected as soon as possible after the pelvic exam; however, this might not always be practical.

If necessary, oral, vaginal, and/or anal swabs should be taken from the victim. The swabs must be air-dried 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 with a moving, non-heated air source 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 can 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. Buccal swabs from the victim must also be air-dried in conjunction with any other wet or moist samples (not including whole blood samples, vaginal washings 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 or briefs because the seminal fluid will drain into these garments (if the assault was vaginal or anal in nature) and seminal fluid tends to dry faster in the underwear. If the underwear has 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 must 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 or the victim. 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 might not provide 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 that might 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 must be collected from the suspect for comparison. These samples include: a buccal swab or a whole blood sample in a purple top "Vacutainer"; 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 evidence from the victim such as hairs, fibers, blood, etc. can be found on the suspect's clothing. External penile swabs should also be collected from the suspect to determine if the victim's DNA is present.

            The key to proper collection, preservation, analysis, and overall usefulness of evidence is open and plentiful communication between investigators, forensic scientists, and prosecutors. 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 might 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 she has a question or a problem on the collection or preservation of evidence.