Mr. Lee’s friends and family assert that his September confession was forced, a dominant view in the Taiwanese media and online forums. They also say they had never heard of Mr. Peng, who they believe is a prop used to create the appearance of Mr. Lee’s conspiring with a Chinese citizen to sow discord in the authoritarian state.

An academic manager at a Taipei community college, Mr. Lee had previously made trips to China without incident. He also regularly chatted online with Chinese acquaintances interested in Taiwan’s transition from a one-party state under martial law 30 years ago to a democracy today, according to Cheng Shiow-jiuan, the director of the Taipei Wenshan Community College, where he last worked.

Mr. Lee also donated money and books to the relatives of rights lawyers imprisoned in the crackdown on civil society by President Xi Jinping of China, the activist’s wife, Lee Ching-yu, said in a March interview.

Ms. Lee attended Tuesday’s sentencing of her husband. In a statement released afterward, she said that “pursuing ideals comes at a cost” and that her husband had been fully aware that by promoting human rights in China he ran the risk of being subjected to forced confession and imprisonment.

”As Lee Ming-cheh’s wife, I’ll say it one more time: I’m extremely proud of everything he’s done,” she added.

Outspoken and defiant, Ms. Lee has become a major figure in the Chinese human rights arena during the eight-month drama. After going public with her rejection of a secret offer by the Taiwan government to work with China via a go-between, she announced in April that she would fly to Beijing to rescue Mr. Lee herself. China canceled the document required by Taiwan citizens to enter the country, effectively banning her entry.

China did, however, allow Ms. Lee to attend her husband’s trial in Yueyang in September. Before leaving for China, she asked the Taiwanese people to forgive him should he say anything negative about Taiwan, since his statements were being made under duress.