The trial comes two months after Lee's stunning resignation from the helm of South Korea's biggest industrial conglomerate.

"I am truly sorry for causing this trouble," the gray-suited Lee said in a calm voice in the packed courtroom. "I will take full responsibility for it and assume a sincere attitude in court."

The 66-year-old Lee also apologized in April when he announced he was stepping down days after he was indicted.

The charges followed a high-profile probe into the conglomerate, of which Samsung Electronics Co. is the flagship corporation.

Lee was indicted on charges of evading 112.8 billion won ($110 million) in taxes and breach of trust.

Prosecutors, however, dismissed the most explosive claim by the former employee — that Samsung maintained a massive slush fund to bribe influential South Koreans.

The tax evasion charge carries a possible sentence of between five years to life in prison, though Lee could serve no time in prison even if convicted because of the leeway given to South Korean judges.