A landmark trial challenging Canada's reliance on solitary confinement is set to begin next month despite a federal government bill that would place new restrictions on the practice.

The B.C. Civil Liberties Association and the John Howard Society of Canada sued the federal government in January, 2015, over the use of solitary confinement in prisons. The two groups said Canada remained committed to a broken and dangerous system that increased inmates' suffering, even as jurisdictions around the world scaled back its use.

However, the Liberal government this week introduced a bill that states a federal inmate can spend no more than 21 consecutive days in administrative segregation, a Correctional Service Canada term for indefinite solitary confinement, unless a warden specifically orders otherwise. Such decisions would be subject to external review. Eighteen months after the bill's passage, that cap would drop from 21 days to 15 days, a threshold recommended in the United Nations' Mandela Rules.

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Read more: Liberal government to impose 15-day limits on solitary confinement

The legislation follows a series of stories in The Globe and Mail about the long-term effects and prevalence of solitary use in Canadian prisons, beginning with a 2014 investigation into the death by suicide of Edward Snowshoe after 162 days in a solitary cell.

But the bill, C-56, fell short of what some prison-rights advocates had expected – they argued it still leaves too much discretion with a federal prison agency that has a long and tragic history of neglecting inmates in segregation.

The trial is scheduled to begin July 4 in B.C. Supreme Court in Vancouver and Caily DiPuma, BCCLA's acting litigation director, said in an interview Tuesday that it's still expected to proceed.

Ms. DiPuma said her organization has concerns about solitary confinement that were not addressed in the bill, but she declined to comment on the specifics, given the impending trial.

The decision to continue with the lawsuit will come as a disappointment to Public Safety Minister Ralph Goodale. On Monday, he expressed hope that his bill – along with previously announced changes to Corrections Canada's internal segregation rules and a budget commitment of $57.9-million to expand mental-health capacity at prisons – would appease the groups behind the lawsuit.

"I obviously cannot comment on outstanding legal proceedings," he told The Globe and Mail, "but I hope those who are engaged in that proceeding will take real encouragement from the fact we've established a new policy, that the Commissioner [of Correctional Service Canada] has established a new directive, that there's new money in the budget and legislation has been tabled in the House of Commons," he said. "I think that sends a very positive signal."

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In December, the lawsuit judge delayed the trial date to give Ottawa time to introduce its long-promised segregation bill. Government lawyers had argued that the bill would render the litigation moot and that to move ahead with the lawsuit before the bill was announced would be counterproductive.

By early May, however, the bill had still not been tabled, prompting Justice Peter Leask to forge ahead with the trial.

While the BCCLA and John Howard Society are withholding specific criticism of the bill as their trial date approaches, Jennifer Metcalfe, executive director of Vancouver-based Prisoners' Legal Services, said it doesn't come close to addressing concerns that many prisoner-rights groups have raised in recent years.

Under existing regulations, a prison warden must review all segregation placements within one working day. If the warden consents to the confinement decision, a Segregation Review Board made up of institution staff examines each segregation placement after five days, and at 30-day increments thereafter.

To Ms. Metcalfe's mind, Bill C-56 only adds yet another review to the process.

"This bill doesn't really change anything substantial," she said. "This is not a cap. This is not a limit. It doesn't say they have to be released at 15 days. At this point it doesn't really change anything except make the warden review each case at a slightly earlier date."

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Her organization has urged the government to prohibit segregation for more than 15 days and ban segregation for prisoners with mental disabilities as well as prisoners under the age of 21. The group also wants an independent adjudicator to be given the power to remove inmates from segregation.

Under the proposed legislation, 15 days would be a presumptive limit that could be disregarded at a warden's whim. External oversight would come in the form of a reviewer rather than a adjudicator.

"A reviewer only has the power to make recommendations," said Ms. Metcalfe. "Without the power to remove someone or to order counselling or other services or access to meaningful human contact, it's pretty empty."

The bill states that prospective reviewers will need to have expertise in "administrative decision-making processes."

Mr. Goodale insisted that the reviewer position will be vital to overhauling segregation practices. "They will be trained, skillful people," he said. "We'll be seeking out the very best. The review has to be real and meaningful. It cannot be token or window-dressing."

Through minor changes to internal policies, Correctional Service Canada has managed to reduce the number of inmates in segregation from an average daily count of 800 three years ago to around 400 today.