The Effects of Green Dry-Cleaning on the Ability to Detect and Obtain DNA from Semen Stains on Three Different Types of Fabrics

The ability to detect and obtain DNA profiles from body fluid stains on clothing is important in solving crimes. However, many crimes are reported after a significant delay and stained clothing is sometimes exposed to water, detergents, and/or other cleaning agents before it is collected as evidence. Research on the effects of water immersion and aqueous-based cleaning methods (e.g. machine laundering, detergents, machine drying) indicates that a number of variables affect whether a stain can be detected post-exposure, including the body fluid examined, the fabric type, and the presence or absence of detergents and agitation. However, the effects of dry-cleaning on body fluid stains are not well understood, despite the fact that many fabrics are “dry-clean only.” Additionally, most of the available information on dry-cleaning is based on the chemical perchloroethylene (Perc) and due to a 2007 ban on Perc, research was needed to examine the effects of available dry-cleaning alternatives. Three dry-clean-only fabrics were stained with semen and submitted for dry cleaning. Two green dry-cleaners were used, one using the petroleum-based DF2000™ and one using the silicone-based GreenEarth® process. After dry-cleaning, the stained fabrics were screened using a 5000 Å Crime-lite® and an acid phosphatase (AP) spot test. The sperm were then released from the fabric and detected using a Christmas Tree stain assay. Regardless of the results of the screening tests, the stains were removed and analyzed for DNA. The DNA was extracted using QIAamp ® DNA Investigator kits, quantitated by qPCR using Quantifiler ® Duo DNA Quantification kits, and genotyped using AmpFlSTR Identifiler ® Plus kits. It was found that dry-cleaned semen stains were often difficult to detect with the Crime-lite® and the AP spot test but that sperm were present in abundance during the Christmas Tree stain assay. It was also found that enough DNA could be recovered to generate full Identifiler® Plus profiles from all samples. Therefore, it is important for analysts to exercise caution when screening dry-cleaned evidence as stains may be missed that carry probative genetic information