TORONTO -- Families of two mentally-challenged men shot dead by police hailed a powerful Supreme Court of Canada decision Thursday that forbids police officers involved in such incidents from having lawyers vet their field notes.

The involvement of lawyers is "anathema" to transparency and public trust in the note-taking process, the court ruled in rejecting police arguments that they should be able to talk to counsel before writing in their memo books.

"Permitting consultation with counsel before notes are prepared runs the risk that the focus of the notes will shift away from the officer's public duty toward his or her private interest in justifying what has taken place," Justice Michael Moldaver wrote for the majority.

"This shift would not be in accordance with the officer's duty."

In separate incidents in June 2009, Ontario Provincial Police shot dead Doug Minty, 59, and Levi Schaeffer, 30. The families spent the past four years arguing against lawyer-approved notes.

Minutes after the decision, Evelyn Minty, 86, fought back tears as she said the battle had been a long, hard struggle but worth it.

"It has helped other families and made police more accountable for what they do," Minty said. "That is what we wanted."

Schaeffer's mother Ruth said the ruling was a necessary step toward ensuring accountability from public servants who wield extraordinary powers.

"I did not do this for my son. My son is dead. There is nothing I can do for my son. I did this because I have grandchildren and other people have grandchildren," Schaeffer said.

"If a police officer cannot even write his notes without consulting a lawyer, then my grandchildren and nobody else's grandchildren are safe."

The 6-3 high court ruling clarifies regulations that govern Ontario's Special Investigations Unit, the independent agency which investigates death or serious injuries involving police.

In dissenting, three justices argued everyone should have the right to consult a lawyer.

Ian Scott, the former SIU director, sparked the battle when he took the unusual step of publicly denouncing the practice of having lawyers vet officers' notes, saying it rendered them unreliable.

The Supreme Court ruling will bolster public trust in police watchdogs and their ability to carry out their mandate, Scott told The Canadian Press.

"It's a huge step forward, an important step forward," Scott said.

"The next step I'd like to see is that the witness officers give their statements to the SIU investigators without a lawyer present."

Julian Falconer, who represented the families, said the cycle of police using guns on emotionally disturbed people must be broken.

"There is a historical recognition that the police use of lethal force...has a profound impact on our social fabric," Falconer said.

"For that, their price (and) their responsibility is to be undeniably and absolutely accountable, and it is sad that these families had to bear the burden, the task, of getting this job done."

Dan Axford, president of the Police Association of Ontario, called the ruling disappointing.

"It differentiates our rights to access counsel from that of all other citizens in Canada," Axford said.

In the decision, Moldaver wrote the "indispensable foundation" for the significant authority entrusted to police is public trust, which can be sorely tested when an officer kills someone.

"Permitting police officers to consult with counsel before their notes are prepared is an anathema to the very transparency that the legislative scheme aims to promote," Moldaver wrote.

In a statement, current SIU director Tony Loparco said the court's clarification of the contentious issue would benefit everyone involved.

"The decision will better assist the SIU in conducting investigations in an independent and transparent fashion," Loparco said.