Can a finding that highway regulation or safety concerns animated a traffic stop be set aside?

A trial judge’s finding that highway regulation or safety concerns was a purpose that animated a traffic stop is a finding of fact. As a consequence, the finding is subject to deference and cannot be set aside by this court unless it is unreasonable or based upon a material misapprehension of the evidence adduced at trial: Brown v. Durham, at para. 27.

Sometimes, a traffic stop may have more than one purpose. However, the mere existence of another purpose motivating the stop, beyond highway regulation and safety concerns, does not render the stop unlawful. But the additional purpose must itself not be improper, or proper but pursued through improper means, and must not entail an infringement on the liberty or security of any detained person beyond that contemplated by the purpose that underpins s. 216(1): Brown v. Durham, at paras. 31, 34, 37-39 and 45.