But the court has nonetheless dismissed the man's appeal, concluding the evidence should still be allowed into the case.
Rajan Singh Mann was convicted for his role in a 2006 kidnapping in the Vancouver area, in part due to evidence the RCMP retrieved from two BlackBerrys after his arrest.
Mann's lawyers argued the RCMP should have obtained a warrant before searching the phones, because such devices can hold vast amounts of highly personal information.
The B.C. Appeal Court says a series of judgments in recent years have made it clear smartphones cannot be searched without a warrant, which means the search violated Mann's charter rights.
However, the court says those rulings weren't in place when police conducted the searches in 2008, so the evidence is admissible.