Substantial deference and tribunal expertise post-Dunsmuir: A new approach to reasonableness review

The Supreme Court recently made clear that judges applying the unified reasonableness standard of review developed in Dunsmuir v. New Brunswick should not approach different types of tribunal decisions with different levels of deference. This has created more problems than it has solved. This paper argues that the law should instead recognize that, within the reasonableness standard, some tribunal decisions are owed more deference than others. Specifically, the law should distinguish between decisions that engage a tribunal's expertise, on the one hand, and decisions for which the tribunal relies on privileged but non-expert insight, on the other. While both should be reviewed deferentially, for reasonableness rather than for correctness, only the former should be accorded substantial deference. The second sets out the paper's proposal, illustrated with the example of credibility determinations in refugee law, and explains how the suggested approach avoids the pitfalls both of the former patent unreasonableness standard and of the current unvarying reasonableness standard.