The Presentation and Examination of DNA Evidence Adduced During Adversarial Trials

This study examines the presentation and examination of DNA evidence in the English Criminal Courts, from the perspective of forensic experts. The methodology involved qualitative analysis of expert perception and opinion, through interview.
Much activity has concerned the contribution of faulty expert evidence to miscarriages of justice, however forensic experts have been largely ignored as sources of valuable data. This study is original in specifically examining their experience.
Criticisms of expert evidence in the English courts are commonly described as having their origins in detrimental effects of the adversarial trial system, however, the position supported by this study is that many claimed detrimental effects are based on misunderstanding of the workings of adversarial procedure.
The study examined experts’ perceptions of challenges they faced in the presentation and examination of DNA evidence, including their duty to offer objective and unbiased opinion. The study determined that whilst experts may give ‘unbiased’ opinion, ‘impartiality’ was practically difficult to achieve because of the different roles played by prosecution and defence experts. Furthermore, a lack of clarity regarding the responsibilities implied by the requirement of remaining ‘unbiased’ meant that experts put different interpretations on their duties in this regard. This study concludes that the policy objectives underlying the concept of ‘unbiased’ should be examined, with a view to better defining appropriate expert responsibilities.
The study investigated experience within court. Interviewees reported similar experiences to those faced by forensic experts reported in previous studies. However, evidence in this study supports the proposition that DNA evidence is qualitatively different from older forensic identification techniques. First, the complexity of DNA evidence magnifies many known trial ‘pathologies’ in terms of presentation and examination. Second, it is fundamentally different in that its probabilistic nature means that experts are forced to present it in a rigorously scientific manner. In this way, not only does DNA represent a new paradigm in forensic identification, but it must inevitably force existing tensions between the law and scientific evidence into the open.
This study found experts to be generally passive in supplying the demands of the judicial process. This has included passivity in the face of legal rulings on how complex DNA evidence should be presented. From an evidential perspective, this is indubitably a judicial responsibility. This study supports the proposal, however, that steps must be taken to engage scientific experts in the scientific aspects of these determinations, if the ‘new paradigm’ of DNA evidence is not to be diluted.
The Government must take a lead in co-ordinating expert bodies towards an integrated approach to complex evidence such as DNA, in the inevitable anticipation that future forensic technologies can only be more complex still. It may do this without infringing the over-riding interests of the adversarial system of justice.