A master of forensic psychology student, Victoria Cooke, simulated a mock criminal trial with 128 jury-eligible participants as members of the jury. The study sought to analyse the cognitive processes of jurors, their attitudes regarding justice and fairness and the effect of gruesome evidence on their verdicts.

``Each juror was provided with a case file from a real murder trial, containing a variety of circumstantial evidence,'' Ms Cooke said. ``The jurors were interviewed to ascertain their attitudes toward justice and fairness, their tendency to think critically and individual motivations to engage in thoughtful activities.''

The study found a juror's cognitive skills and preconceived notions of justice significantly affected their verdicts.

``The fundamental belief of the Australian criminal court system is that jurors are impartial decision-makers, capable of processing evidence and rendering verdicts based solely on the evidence

presented at trial,'' Ms Cooke said.

``It's assumed jurors pay complete attention, withhold judgment until all the facts are in, comply with all the judge's instructions and carefully weigh a host of tangible factors. In truth, not all members of the jury have the motivation to consider each element ... and dissect the validity of each opposing argument, and some bring with them to the court preconceived notions of justice that do not allow them to remain objective and impartial in their verdicts.''