The Retention and Transfer of Spermatozoa in Clothing by Machine Washing

The interpretation of trace findings on spermatozoa on clothing is often problematic, as the manner of deposition may not be readily determined. Particularly troublesome are cases involving complainants who are unable to relate a complete history. Small numbers of spermatozoa may be a result of some type of sexual activity or may be due to an unrelated, innocuous incident. Transfer of spermatozoa between items during machine washing has been theorized as one possible method of indirect deposition. This research was undertaken to determine the likelihood of such transfer. A normal machine wash was simulated in three independent experiments. Pristine items of clothing were washed together with one pair of semen-stained panties. After washing, random samples (n=162) from nine unstained items were examined microscopically. Some spermatozoa were detected on all nine previously pristine items included in the wash loads. Three to eight spermatoza were identified in 16% of the samples. One or two spermatozoa were identified in a further 38% of the samples. The original semen-stained panties were also examined following washing. Although there was no visible staining or acid phosphatase activity, significant numbers of spermatozoa were retained in the original stain areas. The analysis and interpretation of these findings is discussed with reference to current DNA methods.