Knowledge-driven judgements: understanding DNA success rates towards evidence-based triage and reporting strategies

Abstract

In NSW, the process of gathering evidentiary samples for DNA testing has been refined to a predominantly police-based triage, collection and sub-sampling system. The primary exception to this is intimate samples related to sexual assault matters, which are collected by medical practitioners and submitted to the DNA laboratory by NSWPF without subsampling, for examination and analysis. Evidentiary sample collection and sub-sampling is conducted by forensic staff employed by the NSW Police Force (NSWPF). The submitted samples progress through highly efficient laboratory-based DNA testing and reporting procedure, conducted by another government agency, the Forensic & Analytical Science Service (FASS), part of NSW Health Pathology (NSWHP). In 2015, this inter-agency process oversaw more than 40,000 samples per calendar year, from a diverse range of offence types – a number which has grown steadily in subsequent years. Each agency collects and electronically retains data relative to their respective role within the process. Specifically, pre-determined data is shared between the agencies to facilitate result interpretation and reporting. Key performance indicators (KPIs) including turnaround times (TATs) and the number of DNA results reported are monitored to inform administrative and operational decisions within the forensic biology and DNA analytical laboratory at FASS.

In this study, the notion of a ‘successful DNA result’ was explored: a snapshot of average DNA recovery and reported results from commonly defined categories over a 12-month period were scrutinised to establish a correlation between the exhibit type and DNA recovery success rates. The determination of exhibit type and the identification of optimal target areas on exhibits, aligned with the DNA reported result was expected to highlight best practice for sample targeting and ultimately lead to more successful DNA outcomes. This knowledge of ‘success’ will assist prioritised decision making for examiners, with potential to streamline associated training for NSWPF forensic crime scene examiners. The possibility of applying smart software to the operational data was investigated for improved resource allocation and advanced forecasting using machine learning and artificial intelligence. The project also sought to identify and define optimal exhibit and sample terminology to better facilitate data analysis. Finally, this study used the outcomes to investigate whether the workflows for DNA analysis and reporting have evolved sufficiently in tandem with rapidly advancing information and communication technology (ICT) to support the industry’s increasing appetite for a data analytics future.

This project will underpin recommendations for a model of best practice that will optimise the use of metrics for comparison within and potentially across organisations. This will collectively aim to turn DNA testing outcomes and associated information into better probabilistic assessment tools.

Date of Thesis submission	2021
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Chris Lennard (Supervisor), Val Spikmans (Supervisor), Sharon Neville (Supervisor) & Tony Raymond (Supervisor)