Everything clean? Transfer of DNA traces between textiles in the washtub

Abstract

Forensic genetic analysis of items possibly handled by a suspect or a victim is frequently inquired by the law enforcement authorities, since DNA left on touched objects can often be linked to an individual. Due to technical improvement, even poor traces, which seemed to be unsuitable for DNA analysis a few years ago, may be amplified successfully today. Yet, DNA can be transferred to a crime scene artificially or unintentionally without any primary contact between the individual and the object found at the crime scene, the so-called secondary transfer or indirect transfer in general. In this study, "secondary transfer" scenarios with cells and DNA of different origins under wet conditions were investigated. Transfer was simulated as either "washing by hand" in a washtub or as "machine laundry" in a washing machine. As expected, major differences were seen between blood stains and epithelial abrasions. DNA from blood donors could be detected clearly both on the donor and on the acceptor textile, regardless of washing method. Regarding epithelial abrasions, simulating worn clothes, after washing by hand, only little residual DNA was found, and partial profiles were displayed on the donor textile, while transfer to the acceptor textile occurred even less and not in noteworthy amount and quality. Single alleles could be found both on donor textiles and acceptor textiles after simulated machine wash, but no reliable DNA profile could be verified after laundry in machine. Therefore, a DNA transfer from one worn cloth (without blood stains) to another textile in the washing machine seems to be extremely unlikely.

A review of trace “Touch DNA” deposits: Variability factors and an exploration of cellular composition

“…Moisture in the sample or surface also improves transfer of DNA either from the body or an intermediate surface [48], as does introducing friction into the contact [48,65]. This is perhaps consistent with reports of transferred DNA being recoverable from clean clothing items colaundered with used sheets or stained fabrics, as moisture, friction and continuous exposure would all be expected [65,111].…”

Recovery of Trace DNA on Clothing: A Comparison of Mini‐tape Lifting and Three Other Forensic Evidence Collection Techniques

“…Each load of laundry was washed with 70 mL laundry detergent, at 40°C for 70 min, which is the most frequently used washing program for delicate fabrics such as clothing. Similar washing conditions were used by others . The laundry was then air‐dried and packed with appropriate care (gloves, mask) to avoid contamination.…”

Laundry in a washing machine as a mediator of secondary and tertiary DNA transfer

“…Previously, it has been shown that sperm cells have been transferred from one item to another during laundry [7,20,21,22]. However, the possibility of shed epithelial cells transfer, sufficient for STR profiling, through laundry was shown to be unlikely [6]. In reality, a single laundry may contain many clothing articles from several individuals and contain various types of e.Proofing http://eproofing.springer.com/journals/printpage.php?token=ZGH0M... biological material.…”

“…The possibility of secondary transfer of biological material is a major concern in forensic DNA interpretation. With continuously increasing sensitivity of commercially available STR kits, better PCR performance of inhibited samples, along with numerous improvements in collection, extraction and amplification methods, minute amounts of DNA, down to just tens of picograms, are sufficient to obtain a comparable DNA profile (reviewed by van Oorschot et al) [6]. Increased sensitivity makes the probability of detecting a profile from secondary transfer DNA source more likely to occur.…”

“…In a recent study, both laundry by hand and washing machine were examined as mechanisms for secondary transfer of DNA from epithelial and blood sources [6]. The results of these experiments indicated that obtaining a DNA profile from secondary transfer of epithelial cells via machine laundry is very unlikely.…”