The B.C. Court of Appeal on Thursday rejected serial killer Robert Pickton's appeal on six second-degree murder convictions.

Pickton's lawyers appealed his 2007 convictions saying, among other things, that the trial judge made mistakes in his instructions to the jury. But the B.C. Court of Appeal ruled otherwise.

Pickton was convicted of second-degree murder in the deaths of Sereena Abotsway, Mona Wilson, Andrea Joesbury, Georgina Papin, Brenda Wolfe and Marnie Frey.

In a strange twist, the friends and family of some 20 other murder victims, alleged to have been killed by Pickton, want the judge to overturn the convictions.

The reason is because Crown lawyers say they won't pursue a second trial against Pickton in connection to the 20 women if the court upholds his original six murder convictions.

"We would hate to see Pickton actually win his appeal, but we want him to -- only because that is the only way we foresee the other 20 girls getting justice," Lori-Ann Ellis, whose sister-in-law Cara Ellis is among the outstanding cases, told The Canadian Press before the judge's decision.

Lilliane Beaudoin's sister, Dianne Rock, vanished in 2001 at the age of 34.

Beaudoin said she has no choice but to hope that Pickton's convictions were overturned.

"This way, at least I have some kind of hope that there's going to be a second trial and that my sister's case will be in the second trial," she said.

"It's sad to say. Usually I would go for the Crown counsel, but not in this case."

Meanwhile, the Crown has launched a counter-appeal of the judge's decision to split the 26 murder charges against Pickton into two different trials.

At the end of Pickton's 2007 trial, Justice James Williams sentenced the serial killer to life in prison with no chance of parole for 25 years.

The maximum prison term for second-degree murder is 25 years, and what Pickton would have received had he been convicted of first-degree murder.

Police first arrested Pickton in February 2002. The subsequent investigation of his Port Coquitlam pig farm turned into the most intensive forensic investigation in Canadian history.

The investigation was a joint operation between the Vancouver Police Department and the RCMP.

The cost of the first trial is rumoured to be in the hundreds of millions of dollars.

With files from The Canadian Press