BEIJING  Chen Shui-bian, the former president of Taiwan who had been on trial since March on corruption charges, was convicted and sentenced to life in prison on Friday by a three-judge panel. The sentencing was expected, but nonetheless came as a serious blow to the political forces that Mr. Chen had led for decades in opposing the traditional ruling party of Taiwan, the Kuomintang.

Mr. Chen’s wife, Wu Shu-chen, was also convicted of corruption and sentenced to life in prison. They were accused, among other things, of stealing and misusing public money from 2000 to 2008, the time that Mr. Chen was in office. They were both fined a total of $15 million.

Under Taiwanese law, it is mandatory for the trial court to file an appeal in cases involving a life or death sentence, even if the convict chooses not to appeal.

Mr. Chen was the first politician outside the Kuomintang to become president of Taiwan, after he helped create, in the mid-1980s, a pro-democracy movement that opposed martial law and other civil restrictions. Martial law was lifted in 1987, and the island’s first multiparty presidential elections were held in 1996.