Police can search the cellphones of people they arrest under strict conditions, Canada's top court said today.

The Supreme Court of Canada says law enforcement officials can go through the cellphone of someone under arrest as long as the search relates directly to the arrest and police keep detailed notes.

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 whether someone has protected their phone with a password doesn'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 give 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 are 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 said 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 and said that while she trusts police would act in good faith, they aren't in the best position to decide whether the law enforcement objectives outweigh the intrusion on privacy.

The dissenting justices found a warrantless search would be justified by a reasonable suspicion that it was necessary to prevent imminent bodily harm.

Court protecting privacy rights

Privacy lawyer Kris Klein said Thursday's decision puts a heavy emphasis on privacy rights. Combined with last summer's Spencer decision, which found Canadians have a right to anonymity online, Klein says the court has used strong language to protect privacy.

The key, he said, will be how police use the court's guidance.

"I think the starting point is that the state can't look at your cellphone ... it has to be in these sort of special circumstances where, for example, you've been arrested​," said Klein, who teaches privacy law at the University of Ottawa.

For safety reasons, police are allowed to search people under arrest. Klein says what the court is saying isn't going much further when it comes to phones.

The guidance, he said, is when police are going to search a cellphone for a reason directly related to an arrest, "just do it properly."

In a statement, the Canadian Police Association said it was pleased with the "common-sense ruling," although it noted one fear.

"‎This court decision recognizes law enforcement's need for modern investigative tools, while providing effective and reasonable limits to police powers ... though, while pleased today, we do remain concerned that this decision will lead to future litigation‎ and ambiguity."