The Supreme Court of Canada split 4-3, with the minority arguing cellphones and personal computers are "an intensely personal and uniquely pervasive sphere" that needs clear protection.
The majority also found that passwords protecting phones don't carry much weight in assessing that person's expectation of privacy.
"An individual's decision not to password protect his or her cellphone does not indicate any sort of abandonment of the significant privacy interests one generally will have in the contents of the phone," Justice Thomas Cromwell wrote.
Canadian courts have been inconsistent so far in deciding whether police can search the cellphone of someone they're arresting, an issue that raises more privacy issues with the prevalence of smartphones that carry vast amounts of information.
Search done in good faith
In the case of Kevin Fearon, the man who challenged the search of his phone, the court found his rights were violated because police did not take adequate notes on the action, and couldn't say precisely why or how the phone was searched.
Fearon was convicted of armed robbery in a 2009 Toronto jewelry heist. Despite finding the search of his phone wasn't reasonable and breached his rights, the Supreme Court said the search was done in good faith.
The court kept the evidence found in the phone — a photo of a gun and a draft text message referring to jewelry that said "We did it."
Excluding the evidence, the court found, would undermine the truth-seeking function of the justice system. The minority disagreed and would have excluded the evidence because it was unconstitutionally obtained.
The court warned that allowing some narrow searches doesn't given police free rein to go through the phones of everyone they arrest.
"Police officers will not be justified in searching a cellphone or similar device incidental to every arrest," Cromwell wrote.
Further, allowing a narrow search "does not give the police a licence to rummage around in the device at will," he wrote.
"In practice... only recently sent or drafted emails, texts, photos and the call log may be examined as in most cases only those sorts of items will have the necessary link to the purposes for which prompt examination of the device is permitted."
Notes not enough to protect privacy
Searches should be done promptly upon a lawful arrest in order to serve the purposes set out in the ruling, the court said. Police must take detailed notes of what they have examined and how it was searched, and the nature and extent of the search must be tailored to the reason for it.
Police must also have "a valid law enforcement" purpose like:- Protecting the police, the accused or the public.
- Preserving evidence.
- Discovering evidence, like locating additional suspects.
The court noted this is not the only way to make the searches constitutionally compliant, and suggested Parliament may want to legislate how the searches can be done.
Justice Andromache Karakatsanis wrote for the minority that Cromwell's solution isn't an adequate way to counter what would be an extraordinary search power. The minority fears putting the "balancing decision" in the hands of police.
"I doubt not that police officers faced with this decision would act in good faith," Karakatsanis wrote.
But police officers are not in the best position to determine whether the law enforcement objectives clearly outweigh the potentially significant intrusion on privacy, she added.
"If they are wrong, the subsequent exclusion of the evidence will not remedy the initial privacy violation."
The minority found that a reasonable suspicion the search is necessary to prevent imminent bodily harm would justify a warrantless search.