The Supreme Court will hear arguments on Friday about whether a child's behaviour during years of alleged sexual assaults raised legitimate doubts about her credibility.

The case puts a lower-court judge under a microscope at a time when the judiciary's handling of sexual-assault trials in Alberta, Nova Scotia and Quebec has raised fresh controversy about the justice system's fairness toward abuse victims.

The child was in Grade 4 when her stepfather first touched her sexually, she testified. Over the next six years, when she was between 11 and 16, he touched her in similar ways approximately 50 times, and once simulated a sexual act. She was 17 when she testified at her stepfather's trial.

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But Justice Terry Clackson of the Alberta Court of Queen's Bench said there was no evidence that, during those six years, she had kept her distance from her stepfather. He acquitted the stepfather of sexual assault and sexual interference.

"As a matter of logic and common sense," Justice Clackson wrote, "one would expect that a victim of sexual abuse would demonstrate behaviours consistent with that abuse or at least some change of behaviour such as avoiding the perpetrator." The Alberta Court of Appeal threw out the acquittal last year in a 2-1 ruling, and the accused man, known as A.R.D.G. to protect the complainant's identity, appealed to the Supreme Court.

The case highlights whether judges are falling back on discredited prejudices about the conduct of victims after an alleged sexual offence, or whether such "postoffence conduct" can raise legitimate questions, for children and adults. In that sense, it is about the definition of reasonable doubt, and what can give rise to it in the minds of judges. It also contains echoes of the 2016 trial of Jian Ghomeshi in Toronto. The ex-CBC broadcaster was acquitted on the basis of evidence about the three complainants' continued communication with him after the alleged sexual assaults occurred.

"I think the case is an important one, as it will allow the SCC to clarify when judicial reasoning crosses the line into sexual assault myths and stereotypes as opposed to simply applying the notion of reasonable doubt," University of Calgary law professor Jennifer Koshan, who teaches judges about sexual-assault law, said in an e-mail interview.

The Alberta Attorney-General accuses Justice Clackson of drinking "from the poisoned chalice of myths and stereotypes," adding in its written argument filed with the Supreme Court: "Speculative myths, stereotypes and generalized assumptions about sexual assault victims have plagued our system of criminal justice since its earliest days."

The hearing at the Supreme Court comes as the issue of equal justice for victims of sexual offences is pitted increasingly against fairness for those accused. And judges' reasoning in these cases is under the microscope.

For many years, appellate courts in Canada have cautioned judges that sexual assault victims should not be expected to behave in a certain way. Indeed, as Justice Clackson himself put it in his ruling, some may report immediately, while others wait years; some may experience nightmares and other trauma, while some may not. Judges are not permitted to draw conclusions about their credibility based on stereotyped views of how victims behave.

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As in many sexual-assault cases, there were just two witnesses in the case before the Supreme Court: the complainant and the accused. The judge's assessment of credibility was pivotal. But two of the three Alberta Court of Appeal judges who heard a Crown appeal of the acquittal ruled that Justice Clackson had used stereotypical thinking in his reasoning.

"In our view, it is neither logical nor a matter of common sense to expect a child complainant to behave in any particular manner," Justice Marina Paperny and Justice Frederica Schutz wrote in directing that a new trial be held.

But in dissent, Justice Frans Slatter said Justice Clackson was entitled to his reasonable doubt. Justice Slatter set out a list of seven elements that reasonable doubt should and should not contain. "More is required than proof that the accused is probably guilty," he wrote. And if postoffence conduct such as declining grades in school or persistent nightmares can help prove someone is guilty, other types of postoffence conduct may support reasonable doubt, he wrote.

He pointed to the 2016 Ghomeshi ruling by Justice William Horkins of the Ontario Superior Court of Justice: "Each complainant in this case engaged in conduct regarding Mr. Ghomeshi, after the fact, which seems out of harmony with the assaultive behaviour ascribed to him."

Edmonton lawyer Kent Teskey, who is representing the accused man in his appeal at the Supreme Court, said in an interview that while postoffence conduct often "tells us nothing," judges and juries need to be able to use their common sense to determine when it is relevant. If the Alberta appeal court ruling stands, postoffence behaviour would become a no-go zone.