The teenager was lying next to his bloodied sword when the police captured him outside a Toronto massage business where one woman had been stabbed to death and another seriously injured.
The sword was inscribed with a sexist epithet and a note promoting an ideology of violence against women was found in the pocket of the teenager, Oguzhan Sert.
With the evidence stacked against Mr. Sert, he pleaded guilty to murder and attempted murder. But a Canadian judge ruled that the attacks were acts of terrorism, in part because Mr. Sert wanted to send a message that he hated women.
On Tuesday, the judge, Justice Suhail Akhtar, sentenced Mr. Sert — who was 17 at the time of the attack — to life in prison, though he will be eligible for parole after 10 years.
Mr. Sert was sentenced as an adult, which voided a previous ban under Canadian juvenile justice laws against naming him, according to one of his lawyers, Monte MacGregor.
The case represents the first time in Canada that the murder of a woman killed because of her gender has been prosecuted as an act of terrorism, a charge that increases the length of a prison sentence.
In a country that has grappled with recent, high-profile attacks against women, the case underscores how Canada is rethinking the classification of some violent acts as terrorism.
Mr. Sert embraced the ideology of an online group whose members call themselves incels, or “involuntary celibates,” and who disparage women and blame them for denying incels what they believe is their right to sex.
Adherents of the group have launched other attacks in Canada over the years, including a deadly rampage five years ago in Toronto in which a man drove a van into a crowd of pedestrians, killing 10 people and injuring 16 others.
The incel ideology has been linked to the killing or injuring of 110 people in the United States and Canada since 2014, according to Canada’s intelligence agency, which in a report referred to incel attacks as a “growing and concerning area of gender-driven violence.”
Canada has typically reserved terrorism charges for religious extremists inspired by Al Qaeda and similar groups. But the judge overseeing the Toronto case said in a ruling that the defendant “was motivated by the incel ideology and wished to send a message to society that incels were prepared to kill and commit violence.”
Mr. Sert admitted to killing Ashley Arzaga, 24, and injuring another woman, whose name cannot be published under a court order.
After the defendant’s guilty plea, prosecutors asked to have the attacks designated as terrorism to increase his possible jail time. He would otherwise have faced a maximum of 10 years in prison.
Justice Akhtar, in sentencing the defendant, said he had displayed maturity beyond his years and sophistication in planning the attack. He had spent months seeking out videos and other research about misogynistic ideology, the judge said, and rejected the defendant’s argument that he had been “brainwashed” by incels.
“The murder of Ms. Arzaga, captured on video, reflects the evils of that ideology,” Justice Akhtar said, adding that “Mr. Sert did not just murder Ms. Arzaga. He butchered her.”
Mr. Sert’s lawyers argued that there was no evidence that their client wanted to intimidate a large swath of the public and that his ideology did not rise to the level of terrorism.
During an earlier sentencing hearing in October, Mr. Sert, reading from a handwritten sheet of paper, said, “I do not hate women or anyone,” and added that he wished he could “travel back in time and talk some sense into my former self.”
Ms. Arzaga’s sister, who sat in the courtroom for part of the trial and asked prosecutors to be identified publicly only by her initials, provided a victim impact statement that was read in court.
“I think the most emotionally draining part of everything is watching my niece celebrating Mother’s Day at the cemetery,” the statement said.
The country’s handling of the case echoes a growing movement in Latin America to more aggressively tackle the killing of women in the region, which United Nations data indicates reached crisis levels. At least 18 countries have passed laws to protect women by creating a class of homicide known as femicide, adding tougher penalties and bringing greater law enforcement attention to the issue.
In February 2020, Mr. Sert targeted a massage business called Crown Spa, where Ms. Arzaga, a woman he had never met, was working at the front desk, according to the judge who presided over his trial. He pulled a 17-inch knife, described in court as a sword, from beneath his coat pocket and stabbed Ms. Arzaga 42 times.
Her screams sent a female manager racing to the reception area, where Mr. Sert also stabbed her in the chest while yelling misogynist slurs, and sliced off part of her finger. The manager wrestled the sword from the teenager sword and stabbed him in the back, the judge said.
The woman suffered serious injuries to her hands, arm and leg, and, reading from a victim impact statement at the earlier hearing, said she would always “be reminded vividly of the pure evil that lies in the shadows.”
The teenager made it out of the spa and was lying on the pavement with the sword beside him. He had written “THOT slayer” on the sword. THOT is a crude epithet commonly used in the incel community to demean women, according to an expert who testified at the trial.
Mr. Sert also told paramedics after the attack that he wanted to kill everyone in the spa. “I’m happy I got one,” he told them, according to the judge’s ruling.
In his pocket, the police found a plastic bag with a knife-sharpening stone, a driver’s license and a piece of paper that made reference to one of the worst mass killings in Canada’s history.
The perpetrator of that attack, Alek Minassian, a college student, turned incels into a household word after he plowed a rental van into pedestrians on a busy Toronto street in 2018.
Mr. Minassian was sentenced to life in prison with no chance of parole for 25 years, but he was not charged with terrorism.
Perhaps the most high-profile attack on women in Canada was the École Polytechnique massacre in 1989, in which a gunman fatally shot 14 women and injured another 12 people before turning the gun on himself.
Canadian terrorism prosecutions are different from other types of criminal prosecutions. Typically, an accused person’s intent to commit a crime to intimidate and scare the public is part of the standard for assigning guilt, said Leah West, a law professor at Carleton University in Ottawa and co-author of a paper about how forms of extremism like incel violence fit into Canada’s terrorism laws.
Canadian prosecutors must also prove that the accused was motivated by a specific ideology, Professor West said, though the law is not clear about what qualifies as an ideology.
“We have this kind of amorphous term that we don’t really know what it means, and it’s a key element to proving someone’s committed terrorism,” Professor West said.
Still, some legal experts say pursuing a terrorism charge is warranted to underscore how dangerous some ideas can be and what they can cause.
But some women’s groups and anti-violence advocates say that leaning on a terrorism strategy to address attitudes that breed misogyny can obscure the severity of other acts of violence against women that are far more common.
“When a woman is killed by her domestic partner, you still have a dead woman and we don’t ordinarily label that terrorism,” Janine Benedet, a law professor at the University of British Columbia, said, “even though that’s also an expression of sexism and an expression of misogyny.”
