Historically, concerns with jury competence have been assuaged by the celebration of trial safeguards, expressions of confidence in jury abilities, and most recently through initiatives intended to improve the presentation of expert evidence. Whereas trial and appellate judges continue to express confidence in the effectiveness of the adversarial trial and the competence of juries, based almost exclusively on their (individual or institutional) experience, jury researchers have been more attentive to empirical studies of jury performance, particularly how jurors understand complex evidence, probabilities, directions and warnings, and standards of proof.
These empirical studies sometimes identify problems with traditional trial practices though often suggest that problems can be improved (or overcome) through more careful presentation. In response, this article contends that legal assumptions and some of the proposals flowing from empirical research are misguided. It will be argued that inattention to the validity and reliability of many forensic science techniques, along with the failure to provide indicative error rates and attend to limitations, proficiency and contextual bias, means that in many cases expert opinion evidence adduced in criminal proceedings is not susceptible to rational evaluation.