Three other people besides Robert William Pickton were arrested in connection with the murders of Vancouver's missing women, the lead investigator in the case testified Monday.

None were charged with any of the murders.

The information came out at the start of the second week of Pickton's first-degree murder trial for the deaths of six women in New Westminster, B.C., during defence lawyer Peter Ritchie's cross-examination of Insp. Don Adam, the RCMP officer in charge of the investigation.

Lynn Ellingsen and Dinah Taylor were arrested more than a week before Pickton was arrested in February 2002, Adam said. 

But he said Ellingsen's connection was "resolved" after an interview with police.

Adam told the court there was an extensive and thorough investigation into Taylor and Pat Casanova, who was arrested almost a year later in January 2003.

The jury has viewed the RCMP's videotaped interrogation of Pickton, in which Casanova is described as Pickton's friend and police allege Ellingsen was blackmailing Pickton. The jury has heard Ellingsen will testify against Pickton.

Casanova is described as Pickton's friend who helped him butcher pigs. Casanova will also testify during the trial.

'I believe he was deliberately playing head games with me.'—RCMP Insp. Don Adam on Robert William Pickton during his 11-hour interrogation

During the interrogation, Pickton said he and Taylor were very close. When Adam pushed Pickton to tell police what happened at the farm, Pickton said several times that he had to talk to her first.

Adam also said he felt Pickton was "toying" with him during the 11-hour interrogation. 

"I believe he was deliberately playing head games with me," Adam said.

Criminal lawyer Donna Turko told CBC News that Pickton's defence lawyer will want to keep asking questions about other possible suspects in this case.

"It's absolutely essential for the defence, at the earliest time possible, to put in front of the jury the possibility that other persons may be responsible for this crime," Turko said Monday. 

"I think the public and everyone has been wondering, was Mr. Pickton capable of these murders? Was he assisted by somebody, or was he actually an accessory after the fact?"

Plans to search farm before Pickton's arrest

Earlier in his testimony, Adam told the murder trial that Pickton was a person of interest in the disappearance of women from Vancouver's Downtown Eastside, and plans were underway to search his suburban pig farm before his arrest five years ago.

He said police were preparing to get a search warrant when Pickton was arrested and released on an unrelated firearms charge. 

Two weeks later, Pickton was arrested again and charged with the alleged murders of two missing women. He was eventually charged with 26 counts of first-degree murder. In the current trial, which began Jan. 22 in B.C. Supreme Court, he is being tried for six counts of first-degree murder.

Adam also told the jury that the investigation is not over, and, in fact, has become even larger because evidence turned up in this case has led police to other unsolved homicides.

The judge ruled last year that trying all the charges at once would be too much for the jury, so he split the case into two trials, with the second one to be held later. Pickton has pleaded not guilty to all charges.

400,000 swabs of DNA taken

Adam, the Crown's first witness Monday, told the jury he had been determined to search the farm in the suburban Port Coquitlam properly.

"Even as I try to think big, I've been guilty of continually underestimating the incredible amount of resources and money this investigation would cost," Adam said.

"This is the largest, most expensive search that has been done in Canadian policing."

'This is the largest, most expensive search that has been done in Canadian policing.'

—RCMP Insp. Don Adam

Adam said more than 400,000 swabs of DNA were taken as evidence by the team of investigators.

He also said bulldozers were called in to dig up the property, and 383,000 cubic yards (292,825 cubic metres) of soil were sifted for human remains.

"You don't go onto a farm like that and start rushing around as though you are on some Easter egg hunt looking for a hot piece of evidence … you take baby steps."

He also noted that the investigation used up the entire supply of white contamination suits in Canada.

Mountie acknowledges he misled Pickton

The RCMP officer said he misled Pickton during a videotaped interrogation the day after the arrest.

Adam said that included telling the accused he had got hepatitis C from prostitutes, when officers suspected he had actually been infected during a hospital stay.

Adam also said he lied during the interrogation about the amount of blood of one of Pickton's alleged victims that was found in a motorhome on the farm site.