VANCOUVER - Canada's prostitution laws have quickly become the focus of the public inquiry into the Robert Pickton case, not the police investigation that failed for years to catch the serial killer.

Yet another witness Tuesday questioned the wisdom of making sex work a crime.

Kate Shannon echoed earlier testimony that the law and the police officers who enforce it have made life more dangerous for the poor, drug-addicted prostitutes in Vancouver's Downtown Eastside, where Pickton hunted for his victims until he was arrested in 2002.

Shannon, a researcher with the B.C. Centre for Excellence in HIV/AIDS, said police tactics designed to enforce the law push sex workers into dangerously isolated areas, which significantly increases the risks they face.

Changing the law to remove criminal penalties and allow prostitutes to work indoors would change that, she said.

"The current criminalization results in enforced displacement, which as we've seen, both pushes people away from health and support services and increases the risk of coerced sex and violence," Shannon said.

"Being able to allow sex workers to work indoors and in safer indoor spaces would be really important, both for allowing sex workers to have some measure of safety, access to services and reduced exposure to violence."

The hearings were called to examine why the Vancouver police and RCMP didn't catch Pickton when he was murdering sex workers in the late 1990s and early 2000s, as well as the decision by Crown counsel not to prosecute Pickton for attempted murder after an attack on a sex worker in 1997.

Those seemingly narrow terms of reference led to complaints the inquiry wouldn't delve into the larger social questions about why women end up working as prostitutes in the first place and the dangers they face once they do.

But the first two witnesses have demonstrated how difficult it will be to separate the police investigation from those larger social questions.

Last week as the inquiry opened, criminologist John Lowman testified the law encourages police officers to treat sex workers as criminals.

He said that fosters an adversarial relationship that makes it difficult for sex workers to come forward if they're attacked and too often involves harassment or abuse from the officers themselves.

Shannon, who interviewed more than 200 sex workers between 2006 and 2008, found a link between prostitutes who reported having been harassed or assaulted by a police officer and the likelihood they were victims of violence later on.

"It increases both fear of violence, as well as arrest, which can lead to several things, such as rushing a transaction and jumping in a car quickly (without first assessing the risk) or moving to darker areas to avoid police, which then increases vulnerability to violence," said Shannon.

Shannon followed a group of 237 sex workers, interviewing each at least twice during an 18-month period between 2006 and 2008.

Most of those sex workers were in unstable living situations and had been homeless at some point in their lives, and most used drugs such as crack cocaine or heroin. Roughly 40 per cent were aboriginal.

Of the sex workers who participated, 57 per cent said they experienced physical or sexual violence during the study, said Shannon, including assault, rape and abduction.

Working in isolated areas or performing work in cars and alleys, rather than indoors, significantly increased that risk, said Shannon.

The research also indicated that Pickton was well known among Downtown Eastside sex workers, even several years after his arrest.

Nine per cent of respondents said they had been to the Pickton farm in Port Coquitlam and roughly three-quarters said they knew other women who had been there.

Pickton's arrest prompted a massive search of his sprawling farm, where police found the remains or DNA of 33 women. Pickton was eventually convicted of six counts of second-degree murder, though he claimed to have killed 49.

Commissioner Wally Oppal opened the hearings last week, and is expected to hear evidence for months as he prepares a report that will examine what happened and make recommendations to prevent more women from disappearing and being murdered.

Oppal is also conducting a less-formal set of hearings known as a study commission to examine broader issues surrounding missing women, including along the so-called Highway of Tears in northern B.C.