TORONTO (Reuters) - Canada's Supreme Court ruled on Thursday that police may search a suspect's cellphone without a warrant under specific conditions that safeguard the broader constitutional right to privacy.

The 4-3 decision mirrored the deep divisions of lower courts in both Canada and the United States as they try to balance privacy rights in a digital age with law enforcement's need to protect evidence.

The Ottawa-based court said that limited searches were lawful in some circumstances. These include that the arrest itself is lawful; the search is deemed necessary to locate and preserve evidence or catch other suspects, protect the police, the suspect or the public; and police take detailed notes on how they examine the device.

"To summarize, police officers will not be justified in searching a cell phone or similar device incidental to every arrest," Judge Thomas Cromwell wrote on behalf of the majority.

"The weighty privacy interest that an arrested person has in a personal digital device will outweigh the state interest in performing a warrantless search incident to arrest, except in exigent circumstances," the majority opinion said.

In practice, this will mean only recently sent or drafted emails, texts, photos and the call log will typically be available, the court said.

The court's dissenting voices said the decision would result in a breach of privacy and tend to "bring the administration of justice into disrepute."

They noted that other personal devices such as tablets, smart watches, laptop computers and smart glasses would likely be subject to the same treatment.

"Unwarranted searches undermine the public's confidence that personal communications, ideas and beliefs will be protected on their digital devices," they wrote.

The decision was seen by some as a step back for privacy rights, which Canadian and U.S. courts have upheld in most recent cases.

"I have to say I'm surprised given the court's very strong recent privacy record ... I'm surprised that a divided court came out permitting some warrantless searches of cell phones," University of Ottawa law professor Michael Geist said.

"The somewhat complicated conditions that the majority wants to set up aren't really a substitute for a warrant, which offers up a much clearer, more practical approach to providing privacy protection," he added.

In the specific case argued by the court, Kevin Fearon was arrested after an armed robbery. His phone, which was not password protected, was searched and found to contain a picture of the handgun used in the robbery and a draft text message that said "We did it".