Issue estoppel is part of criminal law

The Supreme Court of Canada's decision in R. v Mahalingan 2008 SCC 63, released last Friday, makes it clear that issue estoppel is part of Canadian criminal law playing an indispensable role in ensuring fairness to the accused, avoiding inconsistent verdicts and maintaining the principle of finality.

That said, issue estopple does not mean that every piece of evidence led in a first trial and leading to an acquittal is inadmissible in a subsequent trial on another matter. Only issues necessarily resolved in favour of the accused as part of the acquittal or on which findings were made, even if on the basis of reasonable doubt, are estopped.

An accused claiming the benefit of issue estoppel bears the burden of showing that a particular issue was decided in their favour in the previous proceeding.

The entire Mahalingan decision is worth close reading for counsel involved in matters where issue estoppel may apply.
Issue estoppel is, of course, an integral part of civil litigation preventing the same parties litigating the same issues once finally decided in different context. Last Friday's decision makes the two branches of law consistent -- as they should be.

James Morton
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