He has lied on the stand before, and now a former RCMP officer has had his credibility shredded by a lawyer for the men accused of multiple murders in a high-profile gang trial.

In B.C. Supreme Court on Thursday, Ross Spenard, once a blood-spatter expert investigating a group known as "The Greeks," was thoroughly grilled about how he made mistakes in a separate murder investigation and then covered them up by destroying documents and faking memos.

"You lied under oath," charged defence lawyer Matthew Nathanson.

"Yes," responded Spenard.

"Repeatedly, right?" asked Nathanson.

"Numerous times," said Spenard.

Because of those lies during the 2009 trial of Charlie Rae Lincoln, accused of murdering her two-year-old child, the former cop is currently serving a conditional sentence for perjury.

Spenard is on the stand this week as part of the team investigating murders of people linked to The Greeks, which police call a ruthless drug gang that operated out of a pizzeria in Vernon.

An underling who stole from them was beaten to death, another man was run over by a car, and a suspected informant was shot in the face.

Five members of the gang are on trial for those murders in a high-security Vancouver courtroom.

It was the second meeting for Nathanson and Spenard. It was Nathanson who forced Spenard to admit he hadn't been telling the truth during the Lincoln murder trial.

Spenard had claimed he was not the author of a forensics report that got basic DNA science wrong, claiming that a subordinate wrote it. Spenard then broke down when presented with a draft of that report with his name on it that he thought he had destroyed.

In court Thursday, Spenard admitted that he also ignored orders from a superior to keep a police officer the force doubted was qualified away from crime scenes.

He admitted that he even faked a memo from Insp. Brian Andrews to answer a court order from the trial judge interested in getting to the bottom of the mistakes in the original report.

"A trial judge gave you a direct order, and you didn't even care about that, do you?" Nathanson said Thursday.

"No, I didn't," Spenard answered.

Bringing an admitted liar to the stand was a risk for Crown prosecutors, who need to lead evidence related to forensics in this case. The jury heard the defence imply that if Spenard had lied in the 2009 trial, there's no reason he wouldn't do it again.

"You're lying again to this jury, aren't you?" Nathanson asked.

"No, I'm not," responded Spenard.

"When you testified in the Lincoln case, you used the exact same demeanour," Nathanson said.

"This is how I give evidence," said Spenard.

"Truthful or not?" Nathanson asked.

"Truthful or not," said Spenard.

When approached by a CTV News reporter, Spenard refused to comment, saying, "I've been put through the ringer enough."

Prosecutors are gambling that the jury won't believe their entire case is tainted because of Spenard's history. But the Crown may have bigger problems yet to come: Spenard investigated about 90 homicides, and at least one of those is still going to court.