The rights and interests of Taiwan resident Lee Ming-che and his family were fully protected during the investigation of his crime and subsequent trial on the Chinese mainland, an official said on Wednesday.
Lee, 42, pleaded guilty on Monday in a court in Hunan province to inciting subversion of State power.
"The investigation and trial of Lee was conducted strictly in accordance with the law and legal due process. The rights and interests of the defendant and his family were fully protected," An Fengshan, spokesman for the Taiwan Affairs Office of the State Council, said at a news conference.
Lee"s relatives were informed about the hearing in accordance with the law. Afterward, the court arranged a meeting between Lee and his mother and wife as they requested.
An warned that any attempt to politically manipulate or use the case to smear the mainland"s political and legal systems would prove futile.
In March, Lee was put under coercive measures by the Hunan provincial security authorities after being found engaged in suspicious activities on the mainland.
After Lee was detained, his family was informed and allowed to pass goods to him through a Taiwan-based NGO, even though the official communication mechanism across the Taiwan Straits had been suspended.
Communication was placed on hold last year because the island"s new leader, Tsai Ing-wen, failed to acknowledge the 1992 Consensus, which embodies the one-China principle.
Concerned about protecting Lee"s rights, the mainland-based Association for Relations Across the Taiwan Straits entrusted a Taiwan-based NGO to inform Lee"s wife about the case and pass letters from him to his family, An said earlier. Families can also pass items to Lee, he said.
On Monday, more than 30 people, including domestic and overseas journalists, attended the trial.
Videos of the trial were posted on the Sina Weibo account of Yueyang City Intermediate People"s Court.
Prosecutors accused Lee of involvement in an organization aimed at subverting State power and overturning the country"s fundamental political system through instant messaging services.
According to the indictment, Lee asked members of the organization to exaggerate a number of sensitive issues and make defamatory statements about the Chinese government and the country"s political system.
Lee attempted to overturn State power and the socialist system through unscrupulous distortion of the facts and by fanning public hostility against the government and system, the indictment said.
Prosecutors said the activities had seriously harmed national security and social stability.
"I regarded biased and malicious reports about the Chinese mainland by media in the West and Taiwan as reality, and had no clear knowledge of the mainland"s development, "Lee said in his final statement, adding that his rights had been fully protected during the investigation.
A verdict is pending.
Xinhua contributed to this story.