A witness at the Robert William Pickton murder trial testified Thursday in B.C. Supreme Court in New Westminster that the accused serial killer once spoke about a partner during a conversation about how to kill someone without being caught.

Scott Chubb, whose initial tip to police about firearms owned by Pickton first led them to search the farm, was referring to a conversation he claimed he had with Pickton in 2001.

Scott Chubb's credibility has been under attack by defence lawyers for days.
(CBC)

Chubb said Pickton told him the best way to get rid of a drug addict is to inject them with windshield washer or radiator fluid, because police will just think it's an overdose.

Under cross-examination, he told the court Pickton had mentioned a partner during that conversation.

But he couldn't remember why the term "partner" had arisen, or anything more about a partner.

Defence lawyer Peter Ritchie asked: "Are you sure you're not making this up about a partner? Or making this whole thing up?"

"I'm positive," Chubb replied.

Ritchie asked who Pickton's partner was in the pig butchering business.

Pat, Chubb replied, referring to Pat Casanova, a witness the jury heard last week. Casanova was among three people who were arrested but never charged in the murders Pickton is accused of committing.

The defence has repeatedly tried to divert attention to Casanova.

Although Chubb agreed Casanova was often at the farm helping Pickton butcher pigs and was regarded as a kind of partner, he denied Pickton had ever told him Casanova had injected someone.

But Chubb's credibility has been under attack for four days, as the defence questioned both his motives and the various claims he made to police over the years.

Jury listens to tapes

Earlier Thursday, the jury heard several audio tapes of telephone calls Chubb made to police in the months after Pickton's arrest.

In one, he suggests he has new evidence, saying, "I think I know where Willy has hidden the other bodies," and then threatens to share that information with a local newspaper.

Chubb also threatened to release transcripts of interviews he'd done with the RCMP to the media.

But on Thursday, he admitted he was trying to force police to put him and his family in the witness protection program.

Pickton is facing 26 counts of first-degree murder in connection with the deaths of women from Vancouver's Downtown Eastside. Six of the charges are being dealt with at the current trial. The other 20 charges are expected to be dealt with at a subsequent trial.