A murder in Boston
Please note: As of 1 July 2025, the New Zealand Institute for Public Health and Forensic Science (PHF Science) is the new name for the Institute of Environmental Science and Research (ESR). Research and reports published prior to this date may reference the organisation’s former name.
Abstract
In 2009 D was convicted for the 1990 murder of C in C's own apartment. In a post-conviction review DNA attributed only to D and C (and no others) was found underneath the fingernails of C. At trial, in a hearing for a retrial, and in a pending complaint to the Massachusetts Forensic Science oversight board, the statements of government witness' regarding the meaning of the DNA evidence at activity level were a topic of debate. In this paper, a Bayesian network (BN) evaluation of this evidence is presented. This BN uses the propositions that D was the attacker (Hp) versus an alternate proposition that he was not the attacker (Ha). The alternate, which was inferred from defense questioning, requires that transfer occurred from a social meeting 2 to 4 weeks earlier. The evaluation presented here suggests an LR of the order of 800. This analysis suggests that, while the original testimony may not have been prepared for in a formal manner, it was not misleading to a lay jury.
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