“To a wider TV audience, it is meant to discredit human rights defenders as people who fabricate stories that smear the image of the motherland for their own personal gain or self-promotion,” Ms. Pils said by email. “Over all, it has the effect of giving one a sense that the authorities are in control of the truth.”

The party has long cast dissidents as puppets of shadowy, hostile forces backed by the West. But Mr. Xi has redoubled that effort. A few months after coming to power, he demanded a systematic offensive against Western liberal ideas like constitutionalism, and show trials have been increasingly used to impress such warnings on the Chinese public.

“I hope that other so-called rights defenders and defense lawyers will draw lessons from my example and let this serve as a warning,” Mr. Jiang said in a statement to the Changsha Intermediate People’s Court. “Give me a chance to become a new person.”

The court said a verdict would be announced at a later hearing but did not set a date. As a result of his public confession, Mr. Jiang may earn a lesser prison sentence or even a suspended one.

Born in rural central China, Mr. Jiang, 46, had taken on contentious rights cases for more than a decade. His clients included Chen Guangcheng, the human rights activist who escaped house arrest and fled to the American Embassy in Beijing before receiving asylum in the United States. Mr. Jiang has also represented members of Falun Gong, a banned spiritual sect.

The government rescinded Mr. Jiang’s license to practice law in 2009, but he continued advising dissidents and activists. He was meeting clients even after July 2015, when the Chinese police began a widespread clampdown on rights lawyers and their associates. About 250 people were detained in that crackdown.