VANCOUVER — Marnie Frey called her parents for the last time on her 24th birthday. Lynn, her stepmother, answered the phone to hear Marnie giggling, wheedling for some birthday cash. Mrs Frey was reluctant, knowing that it would be spent to feed her heroin habit.

She told her daughter that a parcel was on its way, with clothes, food and toiletries, things low down on her daughter’s shopping list for life on the mean streets of the Downtown Eastside, Vancouver. The thank-you call never came.

Rick and Lynn Frey would not learn what had become of their daughter until after a frantic search that lasted five years. Her remains were unearthed on a pig farm in Port Coquitlam, on the outskirts of Vancouver. The farm belonged to Robert Pickton, known as “Uncle Willie,” a pig farmer well-known for the parties that he threw for prostitutes and bikers at his quasi- legal drinking club, the Piggy Palace.

Investigators dug up the remains of one woman after another, from body parts to minute traces of DNA, until the count came to 30. Four could not be identified. The other 26 were among the names of 67 women who had disappeared from the Downtown Eastside streets. On Monday Mr Pickton goes on trial for six murders, the only cases in which body parts survive.

Few of the details of the evidence have been made public in Canada, where strict publication bans have muffled preliminary hearings. But what has come to light is grim enough: butchered body parts discovered in a freezer; a woodchipper, confiscated by police, where the women’s bodies were believed to have been disposed of; and the public health warning that the pigs believed to have been fed on human remains were then slaughtered and put into the human food chain — along with, perhaps, human meat itself.

At jury selection, the judge warned potential jurors that what they would hear would be “like a horror movie”. But this time, he told them, they would not be able to switch it off.

But the friends and families of the murdered and missing women are those who are likely to suffer the most trauma. Evidence is expected to take as long as a year to hear. Yet most plan to be there, to find out what happened to their daughters, sisters and friends, and how it was allowed to happen. The women of the Downtown Eastside disappeared gradually, over the course of 20 years, unseen and apparently uncared for by those meant to protect them.

The Downtown Eastside is the poorest postcode in Canada, where life expectancy is less than 40. Its seedy bars and dank doorways shelter the huddled forms of vagrants and junkies, creating a filthy foreground to the gleaming skyscrapers less than a mile up the road. It has the highest rate of HIV infection in North America and is the only place in the developed world where infected women outnumber men. Social workers called the prostitutes here “survival sex workers”. They are selling themselves merely to stay alive.

Rebecca Guno was the first to disappear, in 1983, but no one knew then that she was only the first. Fourteen years later, when Ms Frey’s call never came, Mrs Frey grew worried. When Ms Frey had still not surfaced after four months and local police said that they could not help, Mrs Frey and her sister, Joyce LaChance, travelled to the Downtown Eastside to report Ms Frey missing there. “The police there, they didn’t seem concerned. They said she was an adult and she’d probably taken off somewhere,” Mrs Frey recalls. “They made us think we were the only ones looking for someone missing.”

Infuriated by the police refusal to look for her daughter, Mrs Frey and her sister began their own search. They began to meet other people, like them, looking for their missing loved ones. One woman, searching for her sister, had been refused a missing person report and told to “go put her picture up at the needle exchange”. A man, Wayne Leng, was searching for his friend Sarah de Vries, last seen on a street corner on April 14, 1998, seven months after Marnie’s last call.

Ms de Vries’s theory of what lay behind the disappearances was contained in a journal she left at Mr Leng’s. “Am I next? Is he watching me now?” she wrote. “Stalking me like a predator and its prey? Waiting, waiting for some perfect spot, time or my stupid mistake?” The more Mrs Frey spoke to the street girls, the more she became convinced that Ms de Vries’s theory of a serial killer was right. “The girls told me, ‘There’s this guy who picks up girls in vans and takes them to a farm and they don’t come back. He’s got a woodchipper’,” she said. “Then they’d run away scared and wouldn’t say any more.”

Mrs LaChance suddenly thought of the farm near her home where the Pickton brothers lived. She knew a friend of theirs and had babysat for her children. The sisters relayed their suspicions to the police, who were adamant that there was no serial killer.

Family members lobbied the press and The Vancouver Sun began its own investigation. Mr Leng set up a hotline for tips about the killings and received a call from one Bill Hiscox, a former employee on the farm. He knew a woman who had been inside the trailer where Mr Pickton lived, behind the main farmhouse where his brother, Dave, lived. “She doesn’t want to get involved. She’s kind of scared about it,” he said in the call that Mr Leng taped. “But she told me, ‘Billy, you wouldn’t believe the IDs and s*** in that trailer. There’s women’s clothes out there, there’s purses. You know, what’s that guy doing? It’s, like, really weird’.”

Mr Hiscox also noted a case known to the police, when Wendy Lynn Eistetter, a prostitute, had fled the pig farm, handcuffed, bleeding from the stomach, claiming that Robert Pickton had stabbed her. Mr Pickton, who was also wounded in the incident, was charged with attempted murder but Ms Eistetter balked at testifying and the charges were dropped. Mr Leng handed the tape to police but heard no more about it.

The name Pickton would not come up again until 2002, four years later, when police visited the farm with an unrelated warrant to search for an unlicensed gun. They stumbled upon an asthma inhaler prescribed in the name of one of the missing women and the ID cards of several others. They returned with another warrant and began searching the property, beginning with the slaughterhouse.

In the freezers, they unearthed two five-gallon tubs. Inside were severed hands and feet, and the heads of two women among the most recently reported missing. Both were sawn in half like the carcasses of the slaughtered pigs. One, Serena Abbotsway, had gone missing only a few months after leading a protest march against police inaction over the killings. Much of the evidence may have been devoured long before police set foot on the farm. “It is believed that there is a possibility that human remains were fed to pigs but the risk of disease to those who may have had contact with the meat was negligible,” a 2003 police health study said. “The psychological effects may be worse than the physical.”

Five years and 26 murder charges later, the cases of 39 missing women remain open. Investigators continue to sift through the samples taken from the Pickton farm in search of any trace of those still missing. An internal police inquiry has been ordered but the families are still clamouring for a public one. “If this was a rich community in the West End, all hell would have broken loose,” Rick Frey said. Down on the seedy streets of the Downtown Eastside, a serial killer might no longer be stalking the women but the violence continues unabated. In 2005 Donald Bakker was convicted of the torture and sexual assault of nearly 60 prostitutes, whose ordeals he had taped. None reported the abuse to the police. More than 20 men have been convicted of killing one prostitute each in the Downtown Eastside since 1980.

“What’s more scary, one person killing all these women, or all these men killing just one each?” Kate Gibson, the executive director of the WISH drop-in centre asked.

At the junction of Main and Hastings, known in the Downtown Eastside as Pain and Wastings, I stop to speak to a familiar-looking young working girl. She is Natasha, the sister of Ms de Vries, whose adoption by a middle-class family did not save her from ending up here. Natasha had never met Ms de Vries but came here in search of her after fleeing an abusive boyfriend in Ontario.

But her sister had disappeared only a month before. Now Natasha leads the life that her sister left behind. “We don’t talk about that stuff that happened,” she slurs. “You just gotta keep going.”

Mass murderers:

1609 The King of Hungary ordered the arrest of the Slovenian aristocrat Elizabeth Bathory for the vampiric torture and murder of about 600 young girls

1790-1830 Thug Behram, reputed to be the world’s most prolific killer, is claimed to have murdered 931 victims while the leader of the Indian ‘Thuggee’ gang of assassins

1888 Dubbed the first modern serial killer, Jack the Ripper caused terror in London with his spree of prostitute murders. The exact number of victims is unknown

1957 Police searching the home of Ed Gein in Wisconsin uncovered a wardrobe of clothes fashioned from human skin. He was convicted of killing one person, but probably murdered more. Gein later became the model for Buffalo Bill in Silence of the Lambs

1974-98 Harold Shipman killed an estimated 236 people, while practising as a GP, until he was exposed by a forged will

1995 Rosemary West was sentenced to life imprisonment for the murder of ten young girls, including her 16-year-old daughter in Gloucester. Her husband, Fred, committed suicide before the trial