What is the test for reversing the onus of proof (for alleged Charter violation)?

Whether the trial judge erred in reversing the onus of proof (for the alleged section 8 Charter violation) is a question of law. The “correctness” standard of review applies. That means this court (as an appellate court) is free to replace the opinion of the trial judge with its own. Whether the evidence relied on by the police was sufficient to ground reasonable suspicion and whether the demand was made promptly following reasonable suspicion are questions of mixed law and fact. Whether the trial judge failed to properly consider sections 9 and 10(b) of the Charter are also questions of mixed law and fact. A finding of mixed law and fact by the trial judge should be given deference, absent palpable and overriding error, unless it is clear that the trial judge made some extricable error in principle, Housen v. Nikolaisen, 2002 SCC 33. ANALYSIS Were there reasonable grounds to suspect alcohol in the body and driving within preceding three hours, and did the trial judge adequately address the proof of those grounds?