The Supreme Court has turned down convicted killer Robert Pickton's appeal, meaning the former B.C. pig farmer will not get a chance for a second trial.

The ruling also stamps out the possibility that Pickton's additional 20 murder charges will go to trial. After the Supreme Court ruling was handed down Friday, provincial prosecutors said that the 20 charges would eventually be stayed.

Crown spokesman Neil MacKenzie welcomed the decision and said that Pickton is already serving the maximum sentence.

"In reaching this position the branch has taken into account the fact that any additional convictions could not result in any increase to the sentence that Mr. Pickton has already received."

In December 2007, Pickton was convicted of second-degree murder in the deaths of six Vancouver women: Mona Wilson, Sereena Abotsway, Brenda Wolfe, Marnie Frey, Andrea Joesbury and Georgina Papin.

Though Pickton was initially charged with 26 counts of first-degree murder, the judge decided to split up the charges and put six of them to trial first.

But Pickton's appeal was based on the premise that the presiding judge erred when giving instructions to the jury.

The Crown maintained that that even if the judge had made a mistake, it wasn't serious enough to require a second trial.

The Supreme Court was unanimous in ruling that Pickton got a fair trial, though its members were split 6-3 on the reasons for their decision.

On the sixth day of deliberations in the December 2007 trial, the jury asked the judge if they could find Pickton guilty if they believed he acted indirectly. The judge said they could find Pickton guilty if they found he "was otherwise an active participant" in the killings.

Pickton's defence said the instruction gave the jury the power to convict their client, despite the fact the Crown's case was based on him being the person responsible for the crimes.

In the Supreme Court decision, Justice Louise Charron, on behalf of the majority, wrote that "throughout the trial, the defence by its approach urged the jury to consider that others may have actually killed the victims. An inevitable consequence of going down that road is that the jury would have to be instructed on how this could, if at all, impact on Mr. Pickton's own criminal liability."

Charron said the judge was correct to clarify his instruction to the jury, because his initial charge was confusing.

Additionally, Charron said "realistically, this case was never about whether Mr. Pickton had a minor role in the murder of the victims. It was about whether or not he had actually killed them."

CTV's Janet Dirks said the surviving family members may have a range of feelings about the fact that Pickton will not face a second trial.

Inquiry mulled

Despite legal closure Friday, the B.C. government is still mulling a public inquiry into the case.

Both the RCMP and the Vancouver Police have been criticized for ignoring reports in the 90s that women had been vanishing on the city's rough Downtown East Side.

Marilyn Kraft, whose stepdaughter Cindy Feliks went missing in the late 90s, agreed that an inquiry is necessary. Feliks' DNA was later found at the Pickton farm.

Kraft said that family members first told police in 1997 that Feliks had gone missing, but officers didn't take the claims seriously. In 2001, Feliks was labelled as a missing person.

"So that was four years, which I'm very upset about," Kraft told CTV News Channel from Calgary.

Vancouver deputy police chief Doug LePard has offered an apology to the victims' families and the RCMP have completed an internal revue of their conduct.

"I guess it's better late than never," said Kraft.

"This happens to a lot of young women who are out on the streets ... It doesn't matter what she did, she was still my daughter."

Journalist Stevie Cameron expressed concern that if Pickton won his appeal, the families would have to suffer through a second trial that, if successful, would simply hand him the same punishment again.

"The difficulty is that there are 20 families out there -- in fact, there are more than 20 -- who would really like to see him tried for the murders of their girls," Cameron said.

The first trial took nearly a year to complete and another year of arguments.

Cameron said "it's just a long, arduous thing and I think most families would be okay if it ended today."

With files from The Canadian Press