Open this photo in gallery Sun Qian is a Canadian citizen who is being detained in Beijing.

A Canadian Falun Gong practitioner says she was tortured by Chinese authorities after being framed by her husband, who used her beliefs to turn her in while having an affair with a younger woman.

“I did not, I do not and will not do anything illegal,” Sun Qian told the Wenyuhe court in Beijing on Wednesday, where she stood for a single-day trial 18 months after she was first detained.

Chinese authorities had promised an open-court hearing for Ms. Sun, whose citizenship has drawn attention to her case in Ottawa. Several Canadian diplomats were allowed to attend but The Globe and Mail was barred from entering, as were representatives of European embassies. Ms. Sun’s testimony was recounted to The Globe by her lawyer, her mother and her brother.

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Her trial comes as Falun Gong practitioners in Canada pressure the federal government to intervene. Canadian Foreign Affairs officials have met with her regularly in China, and Foreign Affairs Minister Chrystia Freeland has called the treatment of her and other Canadians in Chinese jails “dreadful.”

“Canadian officials have been seized with Sun Qian’s case since we first became aware of it,” said Stefano Maron, a spokesman for Global Affairs Canada. “Canadian officials have raised this case directly with Chinese counterparts, including allegations of mistreatment.”

Ms. Sun, 52, was once a wealthy co-owner with her husband of a biochemistry company. But on Feb. 19, 2017, a group of men arrived at her Beijing villa and took her away.

She was initially detained in a facility where, she said in court, “the staff didn’t give her even a sip of water or a grain of rice,” her lawyer, Li Jinsong, said. A public prosecutor “insisted that they didn’t do anything like that,” Mr. Li said, but offered neither evidence nor surveillance video.

“Of course they have a video recording. They just don’t want to show it,” he said.

Ms. Sun became a Falun Gong adherent in 2014 and credited the practice for curing health problems. She was eventually charged with “organizing/using a cult to undermine implementation of the law.” It is a charge commonly used by Chinese authorities to prosecute Falun Gong adherents. China made Falun Gong illegal in 1999, and now considers it an “evil cult.”

But Ms. Sun said Wednesday that her husband used her beliefs as a cudgel against her. “She said her husband had an extramarital affair with a 25-year-old woman, with whom he collaborated to seize Ms. Sun’s money and stocks,” said Li Yunxiu, Ms. Sun’s mother.

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After Ms. Sun was arrested, her property and company shares were transferred to her husband, Shen Guangqian. On Wednesday, Ms. Sun accused him of working with friends in the police to arrest her, then falsifying her signature on asset transfers while she was in detention, Mr. Li, her lawyer, added. (A different Chinese court has yet to accept a lawsuit filed against Mr. Shen in late July on that matter.)

Mr. Shen did not respond to repeated requests for comment.

Ms. Sun was the only person to testify in court after authorities denied Mr. Li’s request to cross-examine Mr. Shen and the family’s maid. But the case against her contains errors, he said. An arrest warrant, for example, was dated after Ms. Sun was taken in, "so it’s obvious they forged the application,” he said.

Ms. Sun arrived in court handcuffed and wearing her own clothes. Her family described her as in good health. However, she described mistreatment in detention, including this May when she was shoved to the ground and pepper-sprayed after an argument with a guard, which she said the guard instigated. "They didn’t provide video of that, either,” Mr. Li said.

If found guilty, Ms. Sun faces three to seven years in prison. In court, she called “all the elements and procedures of her case illegal,” her mother said. Ms. Sun said “she believes practising Falun Gong is both legal and reasonable.”

A verdict is not expected for weeks, but Ms. Sun’s 18 months of incarceration have left a mark on the family.

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“Seeing my daughter get detained and suffering through all of this has left me really, really sad,” said Ms. Li, her mother. “Living in a country like this without freedom or human rights, I feel sorry for her. I feel pain.”

But her case "is not a particularly special one,” said Huang Hanzhong, one of a series of lawyers who backed out of representing Ms. Sun after coming under government pressure. "Each year in China there are tons of similar cases being processed in Chinese courts.”

Still, he said, the fact Ms. Sun was brought before a court represents progress. In the past, Chinese authorities responded to perceived ideological threats in ways that were "very brutal and very bloody. They are now expressing this type of hatred in a more civilized way than before.”

China nonetheless maintains a roughly 99-per-cent conviction rate, and Mr. Huang criticized Chinese authorities for failing to abide by their own laws. Ms. Sun’s trial, for example, was meant to be open.

But when The Globe and Mail and European diplomats arrived, a court worker emerged and refused them entry. "We had hoped to let you in, but unfortunately we don’t have sufficient seats in the courtroom. The room is full; there’s nothing we can do,” she said.

That room has, however, accommodated more people in the past. When Ms. Sun’s sister, Sun Zan, came here for a pretrial conference on April 23, it contained three rows of seats. This time, only two remained. Some of the spots were given to Canadian diplomats and family members. The rest were occupied by police and people Ms. Sun had never met.

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They "must have been arranged by the government to fill up the room,” Ms. Sun said.

Meanwhile, numerous police, plainclothes agents and volunteers with the “Office of Comprehensive Management” crowded around the entrance to the court, an unmarked three-storey building in a distant corner of Beijing where goats grazed on roadside bushes. The Globe was told to leave the court entrance to avoid blocking traffic.

“My understanding is that they want to limit the influence of this case,” Sun Zan said.