A police psychologist says the charges laid against four senior RCMP investigators handling the Surrey Six slaying have given the accused a big break to fight their murder charges.

"Behaving in this way now has given defence counsel ... in the Surrey Six case ... a huge lever," Dr. Mike Webster told CBC News.

On Thursday, the force announced four senior RCMP officers involved in the investigation of a 2007 shooting that left six dead in a Surrey, B.C., high-rise are facing a total of 20 charges for obstruction of justice, breach of trust and fraud.

The investigation into the officers began with a report one of the officers, Sgt. Derek Brassington, allegedly had a relationship and impregnated a woman who was a potential witness in the case.

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Photos of an aspiring model said to be involved in a relationship with an RCMP officer and a convicted murderer have been altered to protect her identity. ((CBC))

The woman was the former girlfriend of Dennis Karbovanec, who has pleaded guilty in the Surrey Six slayings, and Jamie Bacon, who is charged with a role in the killings but has yet to stand trial.

No details have been revealed about the offences allegedly committed by the other three officers, Staff Sgt. David Attew, Cpl. Paul Johnston and Cpl. Danny Michaud.

But the special prosecutor has recommended that Brassington and Attew each face charges of breach of trust, obstruction of justice and fraud, while Johnston and Michaud should face charges of breach of trust and obstruction of justice.

Questions raised about RCMP Taser investigation

Webster said the charges against the RCMP also raise questions about the highly-criticized investigation into the death of Robert Dziekanski at Vancouver International Airport because two of the officers charged were also involved in that internal RCMP investigation of fellow officers.

"Any reasonable person would now wonder about other investigations that these particular members have been involved in and I'm sure people are going to start taking a look at them and reviewing them," he said.

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The body of one of the six people who died in the Surrey Six slayings in 2007 is put into a coroner's van. (CBC)

Attew was also the team commander in the Dziekanski investigation and Brassington was the primary investigator.

While they found no fault in the conduct of the officers involved in Dziekanzki's death, the four Mounties involved were recently charged with perjury, following a special external investigation.

Webster said the RCMP has a big credibility problem and senior brass are setting a poor example for the rank and file members to follow.

"My opinion is the organization is rotting from the top down," said Webster.

He notes RCMP Commissioner Guiliano Zaccardelli recently resigned over contradictory testimony he gave in the Mahar Arar investigation.

"It starts at the top. The tone, the bar is set at the top and there's nobody at the top setting the bar. The house needs to be swept clean," said Webster.

Victim's mother saddened by charges

Meanwhile, the mother of one of the Surrey Six victims said she's saddened that criminal charges have been laid against four RCMP officers investigating the gangland slaying, but hopes it won't affect any upcoming trials.

Chris Mohan was one of two innocent bystanders killed in the 2007 gangland slaying. His mother Eileen Mohan said her son deserved better.

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Eileen Mohan says she is dissappointed four RCMP officers involved in the Surrey Six investigation are now facing charges themselves. (CBC)

"These four officers actually acted in a way that the death of my son meant nothing to them," she told CBC News. "I felt really let down by these four officers.

"But I was lifted up by so many other officers and their behaviours and their respect towards me, and I must tell you they are all very much appalled at what these four have done, which makes them all look really bad," she said.

Mohan said she also hopes that new charges won't endanger the Surrey Six investigation or any upcoming trials.

"There's no way that something like this will let — I believe — will let these people walk on technical grounds."

The case will proceed by direct indictment to B.C. Supreme Court where the four officers are scheduled to make their first court appearances July 11.

Report of affair sparked investigation

RCMP Chief Superintendent Janice Armstrong said the officers will likely testify against the accused in the Surrey Six killings, but she wouldn't speculate how the charges might affect the integrity of the investigation and any trials.

"I think that's going to be for the courts to decide," she said.

Armstrong said Thursday the officers also face internal RCMP code of conduct investigations and the force is seeking to have the officers suspended without pay.