Beyond the Rule in Mohan: A New Model for Assessing the Reliability of Scientific Evidence

P. BRAD LIMPERT

ABSTRACT

Although scientific evidence is becoming more important in the legal system, lawyers and judges often struggle to assess the reliability and weight of this evidence. This struggle leads to a concern that fact- finders will overvalue or undervalue information and opinions arising from science. A review of American and Canadian case law on the issue of admissibility of scientific evidence reveals that these concerns are well-founded. The case law indicates that a coherent approach to admissibility remains elusive. The reliability of scientific evidence is evaluated by vague rules, multiple-factor tests, and, occasionally, consideration of general acceptance in the scientific community. There is a more constructive approach to scientific evidence. Uncertainty in scientific evidence can be evaluated systematically. The reliability of scientific information can be comprehensively evaluated by focusing on the uncertainty that arises during each step of empirical hypothesis-testing. Seven types of uncertainty must be considered: conceptual, measurement, sampling, mathematical modelling, causal, testing, and communicative or cognitive. A further analysis of the problem presented by technical and complex evidence reveals that some difficulties are caused by the procedures of the adversarial system. The adversarial system hinders reconstruction of scientific truth and can create a false impression of scientific controversy. These difficulties can be reduced by early, responsive dialogue between opposing experts and by limited use of court-appointed experts.

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Citation: (1996) 54(1) U.T. Fac. L. Rev. 65.
Copyright © 1996. University of Toronto Faculty of Law Review.
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