Robert Pickton takes notes during his trial in Vancouver in 2007. (CBC)

B.C.'s Solicitor General Mike de Jong says he has yet to decide whether he will call an inquiry into the police investigation of Robert Pickton after police admitted they made mistakes.

On Friday, the federal Supreme Court ruled that the serial killer will not get a retrial for his conviction on six counts of second-degree murder.

Pickton was convicted in December 2007 in the deaths of Sereena Abotsway, Mona Wilson, Andrea Joesbury, Brenda Ann Wolfe, Georgina Faith Papin and Marnie Frey. His lawyers appealed the ruling, arguing the judge had erred in his instructions to the jury.

B.C. Crown prosecutors confirmed after Friday's decision that they will stay the other 20 murder charges Pickton is still facing because he has already been sentenced to the maximum time in jail possible — life with no chance of parole for 25 years.

With no more prosecutions planned, many of the families of the women who are the subject of the 20 outstanding charges say their only chance for justice is through a public inquiry.

The decision to call an inquiry lies with de Jong, who said he'll decide soon.

"I think there are very compelling reasons to take a comprehensive look at all aspects of the investigation," said de Jong.

Police admit mistakes

On Friday, both the Vancouver Police Department (VPD) and the RCMP said an inquiry is warranted.

Vancouver police deputy chief Doug LePard, who conducted a review of the VPD and RCMP investigations of the Pickton case, said on Friday morning that police made mistakes before Pickton's arrest in 2002. Pickton was arrested after the DNA of several women who had gone missing from Vancouver's Downtown Eastside was found on his pig farm in Port Coquitlam, B.C.

"I wish to say to the families that we're sorry from the bottom of our hearts that we didn't catch him sooner and protect more women from being harmed," said LePard on Friday. "When faced with the worst ... we should have done better."

LePard promised his 2002 review will be made public in the coming weeks.

Critics of the police investigation say that compelling evidence that a serial killer was at work on the Downtown Eastside was repeatedly dismissed by Vancouver police.

Ernie Crey, the brother of Dawn Crey, whose DNA was found on the Pickton farm, says he is happy Pickton will remain in jail but that he still wants answers to his questions about the police handling of the investigation.

"I'm ready and prepared to live with the outcome of today's decision at the Supreme Court," said Crey. "This man is in jail. He's not going to harm anyone else. His feet won't touch the pavement anytime in the future.

"But for me, that chapter now closed, I'm going to turn my attention to the government of British Columbia and the public outcry for a public inquiry."

Vancouver Mayor Gregor Robertson said he also supports a public inquiry.

“We need to ensure that we draw lessons from this case and do all that we can to prevent anything of this sort from happening again," he said. "I strongly urge the provincial government to launch a public inquiry into the investigation of Vancouver’s missing women.

"There are many outstanding questions, and the families of the victims and the public deserve truth, accountability and reconciliation. To end the process now is unacceptable. The families and loved ones of the missing women deserve closure."