Method of Sampling

The scientist is able to provide objective evidence in terms of the quantity (determined crudely) and quality of the spermatozoa present and may be asked to interpret the results in the context of the case. When providing expert evidence regarding whether vaginal penetration has occurred, the scientist must be able to rely on the forensic practitioner to obtain the samples in a manner that will refute any later suggestions by the defense that significant quantities of spermatozoa, which were only deposited on the outside of the vulva, could have been accidentally transferred to the high vaginal area during the medical examination (7). It is worth noting that there has been no research to support or refute this hypothesis.

Currently, there is no internationally agreed method for obtaining the samples from the female genital area. The following method has (October 2003) been formulated by experienced forensic practitioners and forensic scientists in England to maximize the recovery of spermatozoa while considering these potential problems:

1. Any external (sanitary napkins or pads) or internal (tampons) sanitary wear is collected and submitted for analysis with a note about whether the item was in place during the sexual act and whether other sanitary wear has been in place but discarded since the incident.

2. Two swabs are then used sequentially to sample the vulva (i.e., the inner aspects of labia majora, the labia minora, and the vestibule). Particular attention must be paid to sampling the interlabial folds. Even though traditionally these swabs have been labeled "external vaginal swab," they should be labeled as "vulval swab" to clearly indicate the site of sampling.

Moist stains should be recovered on dry swabs. However, if the vulval area or any visible staining appears dry, the double-swab technique should be used (28) (see Subheading 4.1.1.).

3. The labia are then separated, and two sequential dry swabs are used to comprehensively sample the lower vagina. These are labeled "low vaginal swabs."

4. An appropriately sized transparent speculum is then gently passed approximately two-thirds of the way into the vagina; the speculum is opened, and any foreign bodies (e.g., tampons or condoms) are removed and submitted for analysis. Then, two dry swabs are used to comprehensively sample the vagina beyond the end of the speculum (particularly the posterior fornix where any fluid may collect). These are labeled "high vaginal swabs."

5. When relevant (see Subheading 8.5.3.), a single endocervical sample is then obtained. At this point, the speculum may be manipulated within the vagina to locate the cervix.

The best practice is to use only sterile water to lubricate the speculum, because research has shown that swabs contaminated by some lubricants yield significantly less DNA, and lubricants may have been used in the incident (Newton, M., personal communication, 2003). If doctors decide for clinical reasons to use a lubricant, then they should take care to apply the lubricant (from a single use sachet or tube) sparingly and must note its use on the forms returned to the forensic scientist.

In the process of sampling the vagina, the speculum may accumulate body fluids and trace evidence. Therefore, the used speculum should be retained, packaged separately, and stored in accordance with local policy. If the speculum is visibly wet on removal, swabbing may be undertaken to retrieve visible material. If storage space is restricted, swab the instrument and retain the swabs instead.

In some centers, additional methods of semen collection are employed (5,63,103) in the form of aspiration of any pools of fluid in the high vagina and/or placing 2-10 mL of saline or sterile water in the vagina and then aspirating the vaginal washings. However, vaginal aspirates should not be necessary if dry swabs are used to sample the vagina in the manner described. Furthermore, there are no data to confirm that vaginal washings retrieve spermatozoa more effectively than vaginal swabs.

In exceptional circumstances (e.g., genital injury or age of the examinee), it may not be possible to pass a speculum to obtain the "high vaginal" and endocervical swabs. On these occasions, two dry swabs should be inserted sequentially into the vagina under direct vision, avoiding contact with the vestibule and hymen. An attempt should then be made to comprehensively sample the vagina by gently rotating and moving each swab backward and forward. These swabs should be labeled "vaginal swabs". Unfortunately, in such circumstances, it is impossible to be certain that the high vaginal swab was not contaminated from semen in the low vagina, which could be there because of drainage from external ejaculation.

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