An Environmental DNA Approach to the Isolation of Human Intra- and Extra-Cellular DNA from Large Volumes of Water from Crime Scenes

Abstract

Forensic samples for DNA analysis are limited by physical size and volume as DNA extraction methods require small portions placed into 1.5 or 2.0 mL tubes for lysis. Apart from tape lifting techniques, this precludes large sample areas from being harvested of cellular material by any means other than washing or wet vacuuming. In addition, forensically savvy perpetrators may employ clean-up methods to remove DNA evidence by way of wash basins and sinks, although evidence may be retained within the p-trap of plumbing. Both outcomes still leave forensic biologists with samples incompatible with most commercial DNA extraction methods. Fields of microbiology and ecology have long used environmental DNA (eDNA) collection methods to overcome the similar challenges of sampling biota within large volumes of water or liquid samples. This study is the first application of eDNA techniques to capture such dilute traces of human cellular material from large water volumes using a microfiltration method. The technique was able to isolate human DNA from as little as 100 cells in 1 L of water. While future optimization is required to determine ideal filter specifications, this research demonstrates a proof of concept for forensic application in cases with challenging substrates that can be washed or contain water. This research was conducted under the Murdoch University Human Research Ethics Committee approval 2019/025.