Dealing with DNA Evidence in the Courtroom

A Plain English Review of Current Issues with Identification, Mixture and Activity Level Evidence

Abstract

DNA has played a revolutionary role within criminal justice systems across the world. This paper, while honouring the role DNA evidence has played, nevertheless aims to set out (in plain English in order to make it readily accessible to lawyers dealing with this evidence) some on-going and new key aspects related to the use of DNA evidence in the courtroom. Areas canvassed relate to identification evidence, activity level evidence and DNA mixtures. Specific issues considered include the potential for misunderstanding of DNA statistics both generally and when ‘partial’ match profiles are involved; concerns in regard to underlying assumptions and interpretation of transfer and activity information to determine how and when the DNA was deposited; and a highlighting of a change to the way statistical calculations are made through new software being used across Australia and internationally, including ‘black box’ assumptions that go into those calculations that is particularly relevant to DNA mixtures. This article is Australian-based and some key Australian cases relevant to these issues are considered, however the issues and principles contained within the article are widely applicable within an international context.