The Montreal police investigator who sought the first warrant to track La Presse columnist Patrick Lagacé's cell phone records defended the move on Monday, saying he needed the warrant to determine which officers were trying to hurt Mayor Denis Coderre's reputation.

Normand Borduas, an internal affairs investigator, appeared before the Chamberland commission Monday, when it resumed after a month-long recess.

Led by Quebec Court of Appeal Justice Jacques Chamberland, the commission is looking into police surveillance of journalists.

CBC/Radio-Canada is a participant in the commission.

Officers leaked mayor's traffic ticket

In 2015, Borduas was asked to investigate a tip that two officers had used a computer, without authorization, to print a traffic ticket given to Coderre several years earlier, before he was elected mayor.

He said Lagacé had been given a copy of the ticket, and although the journalist hadn't published anything about it, Borduas said he learned via the mayor's office that Lagacé was asking questions about it.

A Montreal police internal affairs investigator testified he sought a warrant to spy on La Presse's Patrick Lagacé, above, to find out who in the SPVM was trying to sully Mayor Denis Coderre's reputation. (Radio-Canada)

The officer said he believed a copy of the ticket was given to Lagacé in an effort to damage the mayor's reputation, and he said he suspected two crimes had been committed: using a computer without authorization, and breach of trust.

Borduas said he then went to a judge to request a warrant to track Lagacé's incoming and outgoing calls. His request was granted.

The lawyer for the inquiry, Charles Levasseur, established that Borduas asked a judge for the warrant to track Lagacé's calls before filing one to track the calls of the two officers suspected of using the computer to print off the ticket.

Levasseur asked repeatedly why obtaining a warrant to track the journalist's cell phone was a higher priority than getting a warrant to track the calls of the two officers suspected of printing the ticket and passing it on.

Borduas said it was useful to track Lagacé's calls, as it helped identify a third suspect, although he said there was never enough evidence to lay charges.

The officer's testimony is expected to continue on Tuesday.

Mayor's office involved

To obtain a warrant, police need the targeted person's cell phone number, as well as that person's service provider.

According to testimony on Monday, a member of Denis Coderre's staff, Catherine Maurice, gave police Lagacé's cell phone number so they could proceed.

Maurice served as Coderre's press secretary at that time but is now working as his director of communications.

"That it was his press secretary that gave police his cell phone number shows to what point the whole investigation was political," said Projet Montréal Coun. Alex Norris.