More than a decade after Robert Pickton was arrested, his murders are being used as evidence in an effort to overturn Canada's prostitution laws – and make running a brothel a legal business.

While more than 100 women were murdered off the streets of Vancouver – 49 claimed by Pickton – not a single woman has been killed in any of the city's numerous massage parlours, according to criminologist John Lowman.

"What you've done with our system of law is create an opportunity structure that allows serial killers to prey on street prostitutes," Lowman said.

"When it's unmonitored, in dark areas, that's where women are most vulnerable."

Ontario's top court is currently considering an appeal of whether anti-prostitution laws violate sex workers' Charter rights and put them in unnecessary danger. A lower court had already ruled the laws unconstitutional.

Currently, running a bawdy house, soliciting a prostitute and living off the avails of prostitution are illegal. But Lowman, who testified at the landmark hearings, argued that cracking down on bawdy houses drives women onto the street.

An upcoming paper of Lowman's cites research showing 71 per cent of street workers reported being threatened, and 51 per cent had been physically assaulted.

By comparison, only 20 per cent of massage workers had been threatened, 17 per cent physically assaulted – and none had been murdered.

A CTV News hidden camera investigation into illicit sexual services at massage parlours revealed clean, secure rooms – an environment apparently much safer than the street.

Some advocates, such as former sex worker Trisha Baptie, say the only way to keep women safe is to crack down on johns and pimps.

Others, like current sex worker Sue Davis, say the solution is to bring prostitution into a legal environment so women can get basic rights and protections -- and do not have to be afraid of cooperating with police.

"If we're going to treat people as disposable and not investigate crimes against a certain caste of people, they're going to go unchecked," Davis said. "People will die."

The five judges overseeing the case in Ontario are expected to take months to come to a decision, which is then likely to be appealed to the Supreme Court of Canada.

With a report from CTV British Columbia's Jon Woodward