Fast DNA reports for investigative leads in casework practice: An automated workflow for mixture analysis using database searching based on probabilistic genotyping

The Fast DNA Identification Line (Fast ID Line) is a series of software solutions automating the process of DNA profile analysis, contamination checks, comparison with reference profiles, elimination and criminal DNA database comparison, report generation and dissemination of results to law enforcement. The Fast ID Line v1.0 focussed on identifying candidates that could be contributors to single-source profiles or major contributors to mixed DNA profiles.

In this paper, the Fast ID Line was extended to automatically report on mixture profiles with up to four contributors. This software, v2.0, includes extended profile analysis rules, a machine learning model for number of contributors estimation and a probabilistic genotyping model for database searching. Suitability criteria were established for the automatically analysed DNA profiles and reporting of the results.

End-to-end testing using casework data demonstrated that the Fast ID Line v2.0: 1) delivered >80 % of DNA reports within three working days, 2) retrieved 1.9-fold more candidates compared to v1.0 (304 vs 162/777 database searches), and 3) reported 72 % of candidates that were reported in the manual casework workflow.

Police and public prosecution across the Netherlands now make use of the Fast ID Line reports with investigative leads. The automated reports are quickly available, allowing law enforcement to act on DNA findings for intelligence purposes before receiving the expert report. Additional information was provided in only 33% of the expert reports. This indicates that, in the majority of cases, the Fast ID Line results only require a confirmation check by a DNA expert, saving valuable time.