The commissioner heading up the long-awaited public inquiry into the Robert Pickton murder investigations says a key question he wants answered is whether marginalized women like those impoverished victims of the serial killer are truly equal to other members of society.

The inquiry was opened Tuesday morning by former B.C. attorney general Wally Oppal just hours after four more advocacy groups decided to withdraw from the proceedings over concerns about its legitimacy.

Of the original 13 groups granted participant status, only five still plan to take part.

Oppal said he is tasked with examining whether it is acceptable to allow those marginalized women to disappear.

"The question is upsetting. It challenges our fundamental values," he said as he opened the inquiry in Vancouver Tuesday.

The commissioner said the question is necessary to understand the nation-wide crisis of missing and murdered women, and how Pickton was able to get away with killing so many women for so many years without being caught.

"Each woman was loved, and now, each woman is missed. The women were mothers, daughters, granddaughters. Many were mothers. Their deaths and disappearances have caused much grief and that continues to this day," Oppal said.

"Individually the loss of each woman is heartbreaking. Taken together the murder and disappearance of so many women is horrific. It is incomprehensible because of the immensity of the tragedy and it is appalling because of the vulnerability of the victims."

The hearings opened as several groups who withdrew from the inquiry rallied loudly outside of the Federal Court building. The demonstrations spilled out onto West Georgia St., forcing buses on the busy downtown street to be rerouted for several hours.

The groups, many banging drums and chanting, say they were ignored while Pickton was terrorizing women and they still aren't being heard now.

Four advocacy groups dropped out of the inquiry just hours before it began.

The Coalition of Sex Worker Serving Organizations said it deliberated for months before deciding to opt out pre-dawn.

The coalition represents three Vancouver groups that support sex trade workers in Vancouver's Downtown Eastside, the troubled neighbourhood where many of Pickton's victims disappeared from.

Kerry Porth of the Providing Alternatives, Counselling & Education Society (PACE) said that the inquiry is fatally flawed because sex workers were not consulted. Porth also takes issue with the fact her group was not given legal funding, while many government and police agencies were.

"It is undeniable that this process will be extremely adversarial, and without meaningful legal representation, women will not have a strong or equal role to play," Porth said in an email to CTV News.

"It's beyond disappointing that the people whose fate was cast so long ago are not part of the process. Sex workers are being silenced now as they have been silenced so many times before, with dire and devastating consequences."

The inquiry is receiving $2-million in funding from the B.C. government, but a decision not to fund non-profit advocacy groups – many of whom long advocated for the commission – has caused many to leave in anger and frustration.

The Assembly of First Nations announced Tuesday morning it would also not participate because of an "unbalance of provincial funding."

National Chief Shawn Atleo said his group is not confident that the inquiry will result in justice for the families of missing and murdered women.

"We hoped the inquiry would shed light to uncover truths that could help with the healing process for the families as well as to begin to point the way forward so that all women and the most vulnerable have access to justice," Atleo said in a statement.

Victim families still plagued by questions

Though some of the missing and murdered women's families were discouraged by the inquiry's controversial start, there was still hope the questions that have plagued some of them more than 15 years could soon be answered.

Lori-Ann Ellis said she expects to hear "lies and untruths" from the Vancouver Police Department, but is counting on the three lawyers representing the families to wring new details on the investigation of her murdered sister-in-law Cara and other Pickton victims.

"I'm hopeful that we will at least get some answers that we've sought for so long," she said. "That we had to fight for [an inquiry] tells us that there's a lot under the surface, and our lawyers are going to fight tooth and nail to bring that to the surface."

Lawyer Cameron Ward, the only paid counsel for the victims' families, said he hopes to uncover the reason police waited almost five years to arrest Pickton despite evidence pointing to him as a prime suspect.

He also plans to probe the possibility the notorious serial killer did not act alone.

"At the end of Pickton's lengthy jury trial, the jury members themselves had some concerns over whether Pickton, in fact, acted alone. The families share those concerns," Ward said.

Pickton bragged to police about killing 49 women, but was only charged with 26 counts of first-degree murder. Of those, only six went to trial, leaving many families frustrated at the lack of justice for their loved ones.

Lilliane Beaudoin's sister Dianne Rock was among the 20 victims whose cases never saw trial. She said she's hoping the inquiry will finally help her learn the details of her sister's untimely death.

"There was never much told to me," Beaudoin said. "I'm hoping to hear everything here."

Ward is representing 17 families with help from two lawyers who are working pro-bono, while the government is paying 14 lawyers to represent police.

Rick Frey, father of murdered Marnie Frey, says the imbalance does not suggest "a level playing field" for families longing for accountability and answers to their lingering questions.

"We're going to miss a lot of critical information," Frey said. "What we want and would like to see… is the truth. That's all we want."

A long time coming

The inquiry will specifically examine the police investigations of women reported missing from Vancouver's Downtown Eastside between Jan. 23, 1997 and Feb. 5, 2002.

Pickton was arrested in 2002, setting off a massive search of his sprawling farm where investigators found the remains or DNA of 33 women. He was originally charged in the deaths of 27 women -- one of which was dropped for lack of evidence -- and eventually convicted of six counts of second-degree murder in 2007.

Pickton was sentenced to life in prison with no chance of parole for at least 25 years after his 2007 conviction. During the investigation, Pickton bragged to police about killing 49 women.

It took police many years to acknowledge that a serial killer was preying on women in the Downtown Eastside.

Thirteen women disappeared from Vancouver's Downtown Eastside after the city's police force first forwarded information about Robert Pickton to the RCMP, according to an internal police review that spreads the blame between both agencies.

Oppal will also study the actions of Crown prosecutors who stayed charges against Pickton in 1998 after he was arrested for attacking a woman in his trailer.

Families of many of the 26 victims Pickton was later charged with killing say his spree could have been stopped then.

All six women that Pickton was convicted of killing went missing after the 1998 charges were stayed.

Oppal is expected to report to the government by the end of the year as to why the system failed and what should be changed.

So far, the total cost of the investigations and trial for the convicted B.C. serial killer have topped $102 million.

With files from The Canadian Press