In acquitting Andrew MacDonald of having marijuana for the purposes of trafficking, the Appeal Court said evidence about the drug police found in the box should have been excluded because they breached his rights.
"A person who is detained can still consent to answer police questions," the court ruled.
"However, that consent must be one that is informed and given at a time when the individual is fully aware of his or her rights."
Early one morning five years ago, provincial police near Sudbury, Ont., stopped MacDonald for speeding. During the stop, Sgt. Kevin Webb looked through the minivan window and noticed a brown cardboard box in the back.
Suspecting the box contained contraband cigarettes, Webb asked MacDonald what was inside.
McDonald responded the box contained cigarettes, prompting Webb to seek authorization to search the minivan. The authorized search turned up a bag with 310 grams of marijuana, almost $5,000 in cash, and 10,000 unmarked cigarettes.
After a four-day trial, MacDonald was convicted in 2009 of having the marijuana for the purposes of trafficking and handed a four-month prison term. He was fined separately for having unmarked cigarettes, a decision currently subject to a separate appeal.
In quashing the marijuana conviction, the Appeal Court said it was clear police had detained MacDonald for speeding, but shifted gears when Webb began to act on his suspicion about contraband cigarettes.
At that point, the court ruled, MacDonald's charter rights to counsel and against self-incrimination kicked in.
"Webb's question about the contents of the box, flowing from his suspicion that the box contained illegal cigarettes, placed the appellant in jeopardy," the Appeal Court wrote.
"Before answering the question, which had nothing to do with his speeding offence, (MacDonald) should have been advised of his right to consult counsel."
The court found Webb's failure to inform MacDonald of his rights was not a particularly serious charter breach. However, it did find his answer gave police the grounds they needed to search the box and find the contraband.
"The marijuana and cigarettes would not have been found by the police had the appellant not made the self-incriminating response," the court said.
"The heightened concern with proper police conduct in obtaining statements from suspects ... will in most cases favour exclusion of statements taken in breach of the charter."
As a result, the court threw out marijuana evidence and acquitted MacDonald.