The Persistence of Seminal Constituents on Panties After Laundering. Significance to Investigations of Sexual Assault

Abstract

The objective of this study was to determine the degree to which a regular machine washing of semen-stained panties affected semen identification and DNA profiling of the stain. The tests used for semen identification included: 1) the Fast Blue Test for acid phosphatase, 2) microscopic identification of spermatozoa, and 3) the PSA ABAcard® Test for detection of prostate specific antigen (PSA). DNA was analyzed using Polymerase Chain Reaction (PCR) of Short Tandem Repeats (STRs). The DNA fragments were sized using gel electrophoresis. Results showed that compared to control semen stains, laundered stains on cotton panties: 1) had reduced but significant numbers of spermatozoa remaining, 2) still tested positive for the presence of PSA, 3) tested negative for acid phosphatase, 4) retained approximately 43% of their DNA, and 5) produced complete DNA profiles. Compared to control semen stains, laundered stains on nylon panties: 1) tested negatively for PSA and acid phosphatase, 2) retained less DNA (<1% of control levels) and spermatozoa than was observed on laundered cotton, and 3) did not always yield DNA profiles. Given this persistence of spermatozoa on cotton, investigators may be able to obtain the DNA typing profile of a perpetrator of sexual assault even after a victim has laundered their clothes.