Persistence of DNA on clothes after exposure to water for different time periods—a study on bathtub, pond, and river

Abstract

DNA traces on clothes of drowned bodies can provide important evidence for police investigations, especially in cases of suspected suicides or homicides. However, it is generally assumed that the water "erodes" a large part of the DNA depending especially on the exposure time. In forensic casework, DNA of suspects could be found frequently on clothes of drowned bodies after hours, sometimes days of exposure to water. This study was conducted to attempt a general statement about the conditions under which sufficient DNA remains can be expected for molecular genetic analysis. For this purpose, different scenarios were designed including DNA from three to five people, different types of waters (tap, pond, bathtub and river) for various time periods, with higher water pressure, different temperature, and soapy water (bathtub). Epithelial cells and blood cells were mounted on cotton cloths, and the DNA left after exposure was analyzed using the Powerplex® ESX17fast kit. In the indoor experiments, complete profiles could be seen even after 10 min rinsing of clothes under the tap and after 1 week in the bathtub. Outdoors, the results differed considerably between summer and winter as well as between pond and river. The longest exposure time still resulting in a complete profile was 2 weeks for a sample with skin cells in the pond during winter. In summer, the time period for erasing the bulk of DNA was 4 hours regarding epithelial samples and more than 1 day for blood samples in pond and river environments. All in all, the results demonstrate that DNA could still be recovered from clothes exposed to water for more than 1 week.

Mitochondrial DNA Evaluation and Species Identification of Kemp’s Ridley Sea Turtle (Lepidochelys kempii) Bones After a 3-Year Exposure to Submerged Marine and Terrestrial Environments

“…However, few studies of skeletal DNA extractions, human or marine animal, have been conducted with an extended time series or with consistent environmental exposure between samples to evaluate environmental effects on DNA quantity and sequence quality. Previous work has demonstrated the detrimental effect of saltwater on human DNA recovery (Borde et al, 2008;Frippiat et al, 2017;Helmus et al, 2018;Meixner et al, 2020). Our results support the tenant that terrestrial samples generally yield higher DNA quantities than samples experiencing prolonged exposure to marine environments.…”

“…However, these investigations often are hindered by DNA degradation and insufficient quantities of genetic material, which is influenced by time, type of tissue, and the environment. The importance of environmental exposure has been well documented in soft tissues (e.g., blood, saliva); for example, UV light (Hall et al, 2014), high levels of humidity and temperature (Dissing et al, 2010;Al-Kandari et al, 2016), and submergence in fresh or saltwater (Borde et al, 2008;Frippiat et al, 2017;Helmus et al, 2018;Meixner et al, 2020). However, these studies investigated a controlled set of variables in a laboratory setting, rather than field exposures, and often for only days or weeks.…”

Touch DNA: impact of handling time on touch deposit and evaluation of different recovery techniques: An experimental study

“…The entire area of such a sample is likely to contain the DNA of the wearer, while the DNA of the handler is likely to be confined to a small area where the garment was touched. For these reasons, in other papers and in real casework, the wearer was frequently detected as a single or a major component 18,20,21 .…”

DNA transfer in forensic science: A review

“…Further studies have started to address the transfer and persistence of skin derived biological material on washed clothing. DNA deposited onto cotton cloths via rubbing on the neck for 5 s gave full DNA profiles from 40% of cloths held under a running tap (with cold or hot water at different time points up to 10 min) and 56% of cloths submerged in water in a bathtub (with or without soap and at different time points up to one week) [193], but gave only partial profiles from 13% of cloths that were machine washed [192]. Kamphausen et al [192] observed few alleles, if any, on the remaining cloths that were machine washed and similarly few alleles were recovered from co-washed clean cloths.…”