The Supreme Court of Canada has crafted a classic Canadian compromise to one of the most divisive cases on religious freedom it has heard – a sexual-assault complainant who insists on wearing her niqab to testify.

Writing for the majority, Chief Justice Beverley McLachlin said that trial judges can permit a witness to wear the niqab when her evidence is uncontroversial or her credibility is not in dispute.

"If wearing the niqab poses no serious risk to trial fairness, a witness who wishes to wear it for sincere religious reasons may do so," said Chief Justice McLachlin, reasoning that it would show disrespect if one right at stake were ranked ahead of the other.

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"In my view, both of these extremes must be rejected in favour of a third option – allowing the witness to testify with her face covered unless this unjustifiably impinges on the accused's fair-trial rights," she said.

But in a clear illustration of the divisive nature of the niqab debate, two minority factions with polar-opposite opinions took sharp issue with the majority.

One of those factions – Mr. Justice Louis LeBel and Mr. Justice Marshall Rothstein – said a niqab should never be permitted in the witness box because it can handicap the all-important task of gauging a witness's credibility.

The remaining judge, Madam Justice Rosalie Abella, disagreed strongly and warned that niqab-wearing Muslim women may refuse to participate in the justice system altogether if their beliefs are not respected.

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The upshot is that trial judges are being left to decide the niqab issue on a case-by-case basis.

Carissima Mathen, a University of Ottawa law professor, said that the lack of a "blanket rule" means that the niqab issue will be litigated at each trial – and frequently re-litigated on appeal. "This is by no means uncommon, but it certainly leaves more loose ends than a ruling one way or another," she said.

Beverley Baines, a Queen's University law professor, accused the court majority of ignoring mounting evidence that facial expressions constitute a misleading guide to credibility.

Thursday's decision involved a case that began in 2007, when N.S. – a Toronto woman whose name is protected by a publication ban – alleged that her uncle and cousin had sexually assaulted her as a child.

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During their preliminary inquiry, an Ontario Superior Court judge refused her request to testify with her face covered. The case, before a jury, was suspended pending the outcome of the top-court decision.

The N.S. judgment has dealt a tremendous blow to sexual-assault complainants, Prof. Baines said. "In sexual-assault cases, the outcome is foregone: The niqab must be removed when there is a contest," she said. "No defence lawyer worth his or her salt is going to leave this issue uncontested."

She predicted that decision will also quickly prove to be out of touch with courtroom realities. "What underfunded and overworked court is going to traffic in the expensive and time-consuming effort required to set up an alternative to banning the witness from testifying unless she removes her niqab?" Prof. Baines asked.

She said that in using words such as "reconciliation" and "accommodation," the court attempted to conceal the unsatisfying nature of its compromise.

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"A compromised right is no right at all," Prof. Baines said. "While the majority opinion strives mightily to create the illusion – albeit not the reality – that a sexual-assault victim might not have to remove her niqab, no similar effort is devoted to suggesting that a comparable compromise should be expected from the fair-trial rights claimants."

Meanwhile, a lawyer for N.S, David Butt, told reporters in Toronto that his client's religious beliefs are sincere and he is confident they will be carefully considered by the trial judge in the case.

"Sometimes, being a legal pioneer means cutting through forests that others can walk through later," Mr. Butt remarked. "Bring it on – and we'll call our evidence."