Those who know Ilham Tohti have always said he has no desire to break apart China, despite his long-standing effort to call out the country's treatment of a minority population on its far western border.
But on Wednesday, Chinese prosecutors presented written testimony they said came from students he once taught at Central Minzu University in Beijing, where Mr. Tohti worked until he was arrested in January and subsequently charged with separatism, a crime in China.
Mr. Tohti, a member of China's Uyghur minority, has been the most influential critic of China's policies in Xinjiang, the sprawling western region where the largely Muslim group lives. His trial, which is expected to last two days and could result in him being sentenced to a lengthy prison term or even execution, has underscored to what lengths China has gone to silence even moderate voices that stand in opposition to its policies.
Lawyers for Mr. Tohti, 44, have said they believe his students were pressured to testify against him.
"Police asked: What objective does Ilham have? The students answered: He wants to split the country," said Li Fangping, one of Mr. Tohti's lawyers, who was in the Xinjiang capital of Urumqi for the trial.
In the past several years, the region has been rocked by a series of deadly riots and terrorist attacks that have killed hundreds. Blaming radical separatists in the region for inciting violence, Chinese officials have responded with heavily armed soldiers on streets and a broad campaign to restrict religious practices, local dress and movement among Uyghurs.
An economist by training, Mr. Tohti was best known as one of the few people willing to publicly challenge Beijing's often heavy-handed efforts. He ran a website that promoted dialogue between Uyghurs and the ethnic majority Han Chinese, but which Chinese authorities accused of stirring dissent.
In the months following his arrest, he suffered a difficult detention that saw him mount a hunger strike in order to receive halal food. After a terrorist attack in March, he was deprived of food for 10 days. And, in the month before his trial, he was left in shackles and denied warm clothing in a cold cell.
"He looks like he has lost quite a lot of weight. His health does not look good," his wife, Guzailai Nu'er, said in a telephone interview. It was the first time she had seen him since he was taken away; his family was denied all access to him. On Wednesday, Ms. Nu'er and three of his siblings were able to attend the legal proceedings.
She described his treatment in court as "not very good." Prosecutors continually interrupted his answers, she said. "They said, 'No need to explain.'"
Mr. Tohti, she said, proclaimed his innocence.
Prosecutors produced written statements from some of the seven students of Mr. Tohti who were also arrested in January, according to Mr. Li, his lawyer.
When they were first detained, those students offered support for Mr. Tohti, the lawyer said in an interview. But "in the end, the students said Ilham intended to split the country, and they didn't realize it until they had spent some time re-thinking about it," Mr. Li said.
It appeared, he added, that the students had been held in individual cells, unlike Mr. Tohti, who was held in a communal cell. The implication is that they were given better treatment to convince them to turn on their teacher.
Prosecutors also played videos in court that showed Mr. Tohti criticizing Chinese policy and the work of the Xinjiang Production and Construction Corps, the quasi-military organization that wields control over large parts of the region. Videos also showed Mr. Tohti arguing that Uyghurs are not "heirs of the dragon," Mr. Li said. Such a statement would suggest Uyghur people are different from other Chinese.
Those close to Mr. Tohti, however, say he has never advocated separatism, unlike some in his home region.
In April, his daughter, Jewher Ilham, appeared before the U.S. Congressional-Executive Commission on China. A student studying in Indiana, she described Chinese treatment of the Uyghur population – which includes strict curbs on religious observance, dress and mobility – as creating a feeling of being "under occupation."
"My father never speaks about separatism; in fact, he is exactly the sort of person a rational Chinese political structure would seek to engage with in order to address the conditions of the Uyghur people," she said. Instead, she added, his arrest "has driven many Uyghurs to a point at which they can't even imagine that their wholly justified grievances can get any sort of a hearing under Chinese rule."
Reporters in Urumqi Wednesday described a heavy police presence around the building used for Mr. Tohti's trial, and said Chinese authorities had refused Western diplomats entrance to the courtroom, including representatives from the U.S., Germany and Canada.
A spokesman for the U.S. embassy in Beijing called for China to release Mr. Tohti.
"His arrest silenced an important Uyghur voice that peacefully promoted harmony and understanding among China's ethnic groups, particularly Uyghurs," Nolan Barkhouse said. "We stress the importance of Chinese authorities differentiating between peaceful dissent and violent extremism."