Robert Pickton, a former Port Coquitlam pig farmer, was found guilty of six counts of second-degree murder in December 2007 in the deaths of six women. (CBC)

B.C.'s Court of Appeal has upheld the conviction of Robert William Pickton on six counts of second-degree murder, but his case appears to be headed to the country's highest court.

In a split ruling issued on Thursday in Vancouver, two of the three Appeal Court judges agreed that Justice James Williams erred in his final instructions to the jury, but they ruled the mistakes were not serious enough to warrant a new trial.

Justice Ian Donald disagreed, concluding the judge and Crown lawyers created so much confusion over key points of law that the conviction should be overturned.

Pickton, a former Port Coquitlam pig farmer, was found guilty in December 2007 of six counts of second-degree murder in connection with the deaths of six women from Vancouver's Downtown Eastside. He was sentenced to life in prison with no chance of parole for 25 years.

The split decision Thursday means the case will have an automatic right to a hearing before the Supreme Court of Canada.

Both the Crown and the defence appealed the original conviction on various grounds, leading to Thursday's ruling.

Trial should have been held on all 26 charges: Appeal Court

In a separate decision on the Crown's appeal, the three Appeal Court judges also ruled that Williams was wrong to split the trial in two, trying six of the murder counts separately from 20 other charges.

Pickton was charged but never tried for the first-degree murder of 20 other women, many of whom were sex trade workers from the Downtown Eastside.

Should the Supreme Court of Canada eventually rule in favour of the defence and grant Pickton a new trial, the B.C. court ruled the new trial should include all 26 counts.

Pickton, who turns 60 this year, was arrested in 2002 after a lengthy investigation into missing sex trade workers from Vancouver's notorious Downtown Eastside.

In December 2007, after almost two weeks of deliberations, a B.C. jury found Pickton guilty on six counts of second-degree murder for killing Andrea Joesbury, Georgina Papin, Mona Wilson, Marnie Frey, Serena Abbotsway and Brenda Wolfe.

Jurors heard that their body parts were found in buckets or buried on Pickton's pig farm. One witness testified Pickton told him he had butchered women and fed them to his pigs.

Initially the Crown wanted to try Pickton for all 26 counts of first-degree murder, but in a controversial decision, Justice James Williams split off six counts, saying the other 20 charges should be tried at a later date.

Appeals launched by both defence and Crown

In January 2008, following the conviction, Pickton’s lawyers launched an appeal, arguing a new trial for six counts of second-degree murder should be granted.

The Crown launched its own appeal, requesting a new trial on all 26 counts of first-degree murder if the original verdict was overturned, arguing that the judge erred when he separated the cases.

The appeal by the defence focused mainly on the instructions Justice Williams gave to the jury.

It contended Williams made a mistake when he initially instructed the jury they could convict Pickton if they were satisfied he acted either alone or in concert with others in the killings.

Pickton's lawyers argued there was no evidence presented at the trial that Pickton acted in concert with others.

The defence also argued the judge made a mistake when answering a question the jury asked on the sixth day of deliberations and by amending his instructions to them.

The question concerned the issue of whether Pickton could be considered guilty if the jury inferred he acted indirectly. The judge told the jury they could find Pickton guilty even if he didn't act alone, as long as they were convinced beyond a reasonable doubt he actively participated in the killings.

According to the Crown's notice of appeal, the judge's instructions to the jury erred when it came to certain evidence presented in relation to the question of whether the murders were planned and deliberate.