Looking for the pinpoint: Optimizing identification, recovery and DNA extraction of micro traces in forensic casework

Abstract

Many challenges are encountered in the analysis of micro traces such as touch DNA or telogen hair samples. Although DNA typing methods have become immensely more sensitive over the last years, recovery of the minute amounts of biological material in micro traces requires further enhancement. For example felony cases, where an offender oftentimes only contributes minor amounts of touch DNA, separation of victim and offender DNA poses difficulties. Whereas complete sampling of evidence generates admixed profiles, single particle collection is labor- and time-intensive. Besides optimization of identification and collection of bio particles during this study, a novel sampling strategy for enhanced DNA yield as well as success rate but simultaneous avoidance of mixture creation is proposed for tapings in forensic casework. Improvement of another crucial step in micro trace analysis, DNA extraction, involved evaluation of efficiency and DNA recovery of different extraction methods, namely magnetic bead based Maxwell extraction, Chelex, Casework Direct Kit and Investigator Casework GO! kit. Direct lysis approaches seemed to be most suitable for low template traces. Recently developed commercial kits even allow the presence of inhibitors. Improvement of embraced aspects successfully facilitates processing of micro traces in terms of time and labor.