The special probe team suspects that Lee gave or promised 43.3 billion won ($38.3 million) in kickbacks to Park's friend Choi Soon-sil in return for the government's backing of a merger of two Samsung affiliates in 2015.

The business merger was seen as critical to the smooth management succession of the group from ailing Samsung Electronics Chairman Lee Kun-hee to his only son Jae-yong.

Special prosecutors viewed Samsung's donation of 20.4 billion won in 2015 to two sports and culture foundations controlled by Choi as bribes.

Lee has consistently insisted that Samsung's donations to Mir and K Sport foundations were made customarily in compliance with government requests, while its financial support for Choi and her family was forced by the presidential office Cheong Wa Dae.

His lawyers repeated the same claims of innocence throughout the opening hearing.

The lawyers said Lee's instructions to group executives following his one-on-one meetings in 2015 and 2016 with President Park remained unclear. They urged special prosecutors from resorting to presumptions in handling Lee's case.

Lee's lawyers also raised questions over the participation of former prosecutor members of the special counsel team in the court hearing, saying the tenure of the special prosecutors already expired at the end of last month.

The first hearing was finished after one hour amid fierce confrontation between lawyers and prosecutors.

The Seoul district court is expected to give its ruling in late May. (Yonhap)