Testifying in his own defence at his second trial on a rape charge, Alexander Wagar acted out the part of his alleged victim. He sat atop the witness box and demonstrated how the teenage girl was positioned on a bathroom sink during what he said was consensual sex. Crown attorney Janice Walsh called it a "piece of performance art not worthy of belief."

"After he went on the stand, I thought for sure we were sunk in the water," Mr. Wagar's lawyer, Patrick Flynn, said in an interview.

But assistant Chief Justice Jerry LeGrandeur of the Alberta Provincial Court in Calgary saw it a different way. Yes, he said in his written ruling, the testimony from the now 29 year old was "almost the antithesis of what you would expect" in a courtroom. But it was spontaneous, candid in acknowledging memory problems and reflected his personality and the life he had lived as a mostly homeless young man. His demeanour did not undermine his credibility.

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In a case that has drawn national attention to the quality of justice in sex-assault cases – after the first judge to hear the case asked the complainant why she didn't keep her knees together, and then acquitted Mr. Wagar – Justice LeGrandeur's task was to determine whether the prosecution had proved its case beyond a reasonable doubt. That meant assessing whose version of events could be trusted. (The Alberta Court of Appeal threw out the first acquittal, citing "myths and stereotypes" in Justice Robin Camp's reasoning.)

The way Justice LeGrandeur handled his task is raising fresh concerns that the justice system is not working for sex-assault victims; the judge was much more skeptical about the complainant's testimony than he was of Mr. Wagar's.

"I find myself mystified as to how judges make assessments about credibility and the burden of proof, and I am no further ahead after reviewing the recent decisions that have come from the courts," Constance Backhouse, who holds the chair in sexual-assault law at the University of Ottawa, said in an e-mail after reading the Wagar ruling.

"It seems to me that it was simpler in the 19th century, when judges and jurors simply disbelieved sexual-assault complainants as a matter of course. The legal and judicial analysis may have changed, but the results on the ground in the 21st century do not seem to be significantly different."

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Kim Stanton, the legal director for the Women's Legal Education and Action Fund, said the complainant had shown courage in facing the system for a second time, particularly after the "demeaning treatment" from Justice Camp.

"The criminal justice system is a very difficult place for sexual-assault complainants. The high burden of proof and the presumption of innocence operate to protect the accused, and these protections are important," she said.

"Sexual-assault trials often focus on the credibility of witnesses and the benefit of the doubt always lies with the accused. However, most survivors do not report their assaults and the experience of the complainant in this case is unlikely to increase the reporting rate."

The key question in the case was whether the Crown had shown that the sexual encounter at a house in 2011 happened without the complainant's consent.

Justice LeGrandeur said he had a reasonable doubt, based in part on what the complainant, then in her late teens, had told Calgary police when she reported the encounter. She had had a verbal spat with Mr. Wagar's brother Lance, who berated her for having had sex with his brother. "I wanted to do it," she told him, according to her own statement to the police.

In her courtroom testimony, she explained that she "was just trying to shrug it off, not to feel what I was feeling."

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But Justice LeGrandeur dismissed her explanation. "It is evidence directly from her mouth that identifies her actions as voluntary. This evidence strikes at the very heart of her assertion of non-consent and severely undermines it."

It was not the only problem Justice LeGrandeur found with her testimony. He also said she had been inconsistent and evasive in several places, for instance, on how much alcohol and drugs she had ingested before the incident.

Deborah Hatch, a criminal-defence lawyer in Edmonton, speaking generally and not about the specifics of the Wagar case, said that the standard of proof beyond a reasonable doubt is justifiably high. "We would each expect, and be entitled to, no less if we were charged with a crime."

Mr. Wagar was denied bail while waiting for his first trial and again while waiting for his second trial, amounting to 17 months in total, Mr. Flynn said. "Some people get disadvantaged, particularly if they're homeless. He didn't have anyone who could put a surety for him."

Justice Camp is now facing dismissal from a disciplinary body, and Dr. Stanton, speaking for a coalition of feminist groups, said Justice Camp has lost the public's confidence, and this week's acquittal does not change that.