Enhancing fairness in DNA jury trials

Controversies over how the law should regulate the presentation of expert testimony on DNA forensic science were explored in an experimental study comparing traditional oral with audiovisual presentations. Pre-trial DNA knowledge assessed in 3611 jury-eligible Australians was limited. From this group, 470 citizens watched a simulated homicide trial containing a cognitively-sequenced generic tutorial on DNA and inculpatory random match probabilities. The expert tutorial significantly improved DNA knowledge, irrespective of the mode of presentation. Given clear and well-sequenced complex information, lay jurors dealt competently with it. Only jurors with low DNA knowledge who were exposed to orally presented evidence were susceptible to the 'white coat syndrome'. The multimedia tutorials were not unduly persuasive, but effectively facilitated decisions by citizens whose comprehension of the scientific evidence was lowest, bringing their verdicts in line with those whose understanding of the evidence was most accurate. Enhanced DNA knowledge increased scepticism about experts and reduced convictions. This model tutorial will be useful to train forensic scientists who serve as expert witnesses, and to assist legal counsel and judges to convey relevant DNA information more effectively to jurors. These results will aid courts and policy-makers in adopting procedures to enhance justice in criminal cases in which DNA is introduced.