He had refused food in protest over what he says is political persecution by his successor, Ma Yingjeou, Taiwan's current president.
The three-day hearing is aimed at allowing the judges to determine the facts of the case with Chen and his lawyers, before both sides argue about guilt or innocence.
"The prosecution's credibility is in question as it keeps changing the content of the indictment and the amount of the money involved," Cheng Wen-lung, his lawyer told the court.
He argued that prosecutors failed to provide sufficient reasons when they added two new charges - extortion and influence peddling - against Chen in another hearing last month.
Ten people, including Chen's wife, Wu Shu-chen, their son and daughter-in-law, have admitted to their roles in the case.
Wu admitted to wiring $2.2 million abroad but said the money was a political donation, not a bribe.
She also said a businessman involved in a land deal wired $5.88 million to her brother's overseas bank accounts.
Wu said her husband had no knowledge of the wired funds.