Men who sabotage condoms may turn an otherwise consensual act with a woman into sexual assault, and women who lie about using birth control have been left with some uncertainty about whether they, too, could face charges, under a Supreme Court ruling yesterday on deception before sex.

The court was unanimous that Craig Hutchinson of Nova Scotia was guilty of sexual assault for poking pin-sized holes in condoms because he hoped to keep his girlfriend from leaving him by getting her pregnant. His fraud carried such a risk of harm it nullified her consent, four of seven judges said. (She did become pregnant, but left him and had an abortion.) The risk to a woman who does not want to get pregnant is as serious in its way as the risk of HIV transmission from a partner who committed deception by failing to disclose their disease, the majority said.

"The concept of 'harm' does not encompass only bodily harm in the traditional sense of that term; it includes at least the sorts of profound changes in a woman's body — changes that may be welcomed or changes that a woman may choose not to accept — resulting from pregnancy," Chief Justice Beverley McLachlin and Justice Thomas Cromwell wrote, supported by Justice Marshall Rothstein and Justice Richard Wagner.

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Other deceptions would have to carry a risk of equal harm – to an unwanted pregnancy or Hiv transmission – to merit charges of sexual assault, the majority said. "Financial deprivations or mere sadness or stress from being lied to will not be sufficient." Whether the court would limit that harm to bodily harm, or whether men who had tried to avoid fatherhood could prove a substantial level of harm, was the subject of debate in the legal community.

Peter Sankoff, a specialist in criminal law at the University of Alberta, said that psychological harm could in rare cases be a foundation for a future sexual assault claim by a man, say, whose condoms were sabotaged by a woman so she could have a baby. In a series of tweets, he said he knows many men who experienced an unwanted child, and as a result "spiralled downward" psychologically.

Others, including Michael Plaxton of the University of Saskatchewan law school, Sonia Lawrence of York University's Osgoode Hall Law School, and Luke Craggs, the lawyer for Mr. Hutchinson, disagreed, saying the court would limit charges to cases where there was bodily harm.

"My preliminary view is that the decision seems to have been carefully written such that women who lie about birth control don't have the same jeopardy," Mr. Craggs said in an interview. Mr. Hutchinson was found guilty at his trial and sentenced to 18 months in jail, but had been free on bail awaiting the Supreme Court ruling.

A man with unwanted paternity would have to show the same level of harm as a woman experiences from an unwanted pregnancy, said Elizabeth Sheehy, who teaches law at the University of Ottawa. "It would be a tough case to make. I don't think it's impossible. I think it's pretty remote. Would it be different if a man had repeatedly communicated his vulnerability in that regard and had his wishes deliberately thwarted? I don't know – you'd be making new law here."

In previous rulings, the Supreme Court has upheld aggravated sexual assault findings where individuals did not disclose that they have the Hiv virus – because it carries a "significant risk of serious bodily harm." But the rulings on Hiv disclosure, the court's majority said on Friday, "did not foreclose the possibility that other types of harm may amount to equally serious deprivations." It could have said "bodily harm." It just said "harm."