Canada's top court yesterday upheld six murder convictions of a pig farmer accused of butchering women and feeding them to pigs in what police have referred to as the country's worst serial killer case.

Canada's Supreme Court was unanimous in ruling Robert Pickton's right to a fair trial was not affected by the trial judge's final instructions to the jury, although they split 6-3 on the reasons.

At the end of an 11-month trial, Pickton (60) was convicted of murdering six prostitutes in 2007 and sentenced to life in prison with no parole for at least 25 years for six counts of second-degree murder.

The Vancouver, British Columbia, pig farmer appealed his conviction, saying the judge gave improper instructions to the jury when they asked, on their sixth day of deliberations, whether they could find Pickton guilty if they inferred he did not act alone.

The trial judge said if they found Pickton “was otherwise an active participant” in the killings, they could find him guilty.

Pickton's defence argued the judge gave the jury an avenue to convict their client without giving them a chance to defend him properly as the prosecution's case rested on Pickton being the only one responsible for the crimes.

Justice Louise Charron said iyesterday that the judge's instructions were proper.

The decision comes more than 10 years after a series of stories in a Vancouver newspaper began to link the disappearances of women from the city's darkest corners. Pickton was arrested in 2002.

Pickton is also charged in another 20 deaths that haven't gone to trial. Pickton and his brother used to throw parties at the hog farm in a barn they dubbed “Piggy's Palace.” Investigators have said they were drunken parties with prostitutes and plenty of drugs. Pickton's brother has not been charged in the case.