HALIFAX -- The Nova Scotia Court of Appeal has ordered a new trial for a high-profile Halifax lawyer sentenced last year to three years in prison for sexually assaulting a 19-year-old woman.

In a written decision released Friday, Justice David Farrar concluded the judge who heard Lyle Howe's case in May 2014 was mistaken when he told the jury the complainant was unconscious when she engaged in sexual activity with Howe.

This was a key point in the case because, under the law, an unconscious person is incapable of giving consent to a sexual act.

According to Farrar's judgment, the trial judge instructed the jury: "Even if she expresses her consent in advance ... it is not possible for an unconscious person to satisfy the requirement of actual, active consent throughout every phase of the sexual activity."

Farrar's decision says the Crown's position and evidence presented at the trial gave no indication that the complainant was unconscious at the time of the offence.

"(The complainant) did not say that she didn't consent to the sexual activity," the judgment says. "But rather, she testified that she could not recall consenting to the activity. It was not the position of the Crown nor was there any direct evidence that (the woman) was unconscious during the sexual activity."

Farrar says this misunderstanding was probably behind the trial judge's refusal to instruct the jury on the defence's position that Howe had an "honest but mistaken belief" that the woman had consented to sex on March 20, 2011.

There was substance to Howe's claim that the complainant did and said things that led him to believe she was consenting to sex, Farrar wrote.

"In my view, there was clearly an 'air of reality' to the defence that it was reasonable for the appellant to have believed that the complainant was not so severely intoxicated that she was incapable of consenting to sexual activity," Farrar wrote in a 21-page judgment.

The judgment says trial judges are duty-bound to present all defence positions that meet the "air of reality threshold" to the jury.

Farrar says the trial judge also failed to instruct the jury about Howe's mistaken-belief defence even after the Crown cited the judge's error following his initial charge to the jury.

At his trial, he testified he had consensual sex with the woman, but the Crown argued she was so intoxicated that she was incapable of giving consent.

On May 31, 2014, Howe was convicted of sexual assault but he was acquitted of administering a stupefying drug to facilitate a sexual assault.

The case sparked protests from activists who said it reflected the justice system's bias against black men like Howe.