The RCMP could have tried several tactics to advance a case aimed at pinning murders of Vancouver sex workers on Robert Pickton years before he was arrested, the Mountie who was the first to probe the pig farmer's gruesome crimes has acknowledged.

A lawyer representing the Vancouver Police named off a list of those potential actions as he questioned now-retired Staff Sgt. Mike Connor, who concluded four days of testimony Thursday at the missing women inquiry.

"I want to suggest to you some steps that could have been taken in the investigation in August 1999, but were not taken," said lawyer Tim Dickson, after describing the body of evidence Connor had amassed up until that point.

Dickson said Mounties at the Coquitlam detachment could have conducted an undercover operation on Lynn Ellingsen, a sex worker who had apparently seen Pickton butchering a woman in his Port Coquitlam, B.C., farm.

Connor agreed, noting just such a plan had been in the works but was not carried out before he was promoted and transferred off the case.

Another undercover operation could have been implemented with the help of Bill Hiscox, who had told police that Pickton was storing bags of women's bloody clothing, purses and identification as "trophies."

The informant, who sourced his tips to a friend of Pickton, said the farmer even bragged about disposing bodies. Dickson said officers could have asked Hiscox to help open up Lisa Yelds, who hated police, to get it on record first-hand.

The lawyer said the investigative team could have also conducted polygraph tests on each of three other informants who offered up grisly details about the happenings on the farm.

"And there could have been more surveillance on Pickton," Dickson said.

"Agree with that one, that's correct," Connor said.

Connor also said that had he known there was talk of bodies being disposed in barrels by Pickton, he would have dispatched a search at the Vancouver recycling plant where they were sent.

Work on the case was limited after Connor handed off the file.

Ellingsen was re-interviewed by police, new aerial photographs of the farm were obtained and Pickton was ruled out as a suspect in a separate investigation of serial murders in B.C.'s Fraser Valley, Dickson said.

Nothing became of a two-hour long interview that two RCMP constables conducted with Pickton two years before his eventual apprehension.

"You accept ... that is far too little progress in two and a half years on a file of this seriousness?" Dickson asked.

"Yes," Connor replied.

"And you agree that the information pointing to Pickton was so compelling, and the allegations so serious, that a major sustained investigation needed to be pursued to either confirm or eliminate that information?" said Dickson.

"A sustained investigation would be required," said Connor.

"And that just wasn't done?"

"No," said Connor.

Pickton was arrested in February 2002 when an unrelated tip about illegal guns on his property prompted a massive search that turned up personal belongings and the DNA of 33 women.

Connor had believed the man was responsible for multiple murders as far back as five years earlier.

He and a partner were the first officers on the scene of a brutal knife attack by Pickton against a sex trade worker in March 1997, where charges of attempted murder and forcible confinement were laid but then dropped.

Even after his transfer, the officer conducted his own surveillance upwards of 30 times on the farm after midnight. He also phoned the joint RCMP-Vancouver Police task force into missing women trying to convince investigators to push Pickton up the list of suspects.

Connor has testified he felt his own evidence was too weak to trigger a search warrant or wiretap on the farm because he just couldn't "catch the break" that was required. Had he needed more resources from the force, he said he's certain he would have received them.

The inquiry is attempting to determine why the serial killer was not captured sooner.

Pickton was convicted of murdering six women, although charged with killing 26. He told a police informant placed in his jail cell that he had murdered 49.