The importance of evaluating findings given activity level propositions in order to avoid misleading evidence

ABSTRACT

The advancement of DNA technology comes with the increased sensitivity of amplification systems, where DNA traces are routinely detected without a known biological source. These systems also have increased discriminating capacity, providing larger likelihood ratios (LRs) when a corresponding DNA profile is observed. Questions in court are shifting from identity to transfer mechanism, where the presence of an individual’s DNA is conceded by both parties, but the activities that led to its deposition is in dispute. One way of handling propositions developed at the activity level is with the use of graphical structures known as Bayesian Networks (BNs). The following is an evaluation of a case, given activity level propositions, through the application of BNs. Alternative case findings will be explored for the given scenario to show the potential value of the DNA evidence for different outcomes within the broader case context.

KEYWORDS:

• Activity level propositions
• evaluative reporting
• Bayesian Networks
• likelihood ratio
• DNA transfer
• DNA interpretation

Acknowledgements

Thank you to the National ANZFSS Executive, ANZFSS SA Branch and Forensic Science SA for funding and support to attend the 24th International ANZFSS Symposium and to present this work. Thank you also to Duncan Taylor and Julianne Henry for proofreading this article.

Disclosure statement

No potential conflict of interest was reported by the author.