Appeals for the bribery case against Samsung heir Jae-yong Lee involving the former president have begun on Thursday in Seoul, South Korea.
The 49-year-old was convicted of bribery earlier this year in August and sentenced to five years in prison.
Lee and his lieutenants were charged with bribing former president Park Geun-hye's friend to get support for a controversial merger that strengthened the Samsung scion's control of the conglomerate.
Prosecutors and defence at the appeals both argued for the lower court's sentence to be overturned. Earlier, prosecutors demanded a 12-year sentence, while Samsung has consistently denied the payments were bribes.
Arguments revolved around memos written by Park's aide and whether payments made to the president's friend, a civilian, constituted bribery.
The memos, written by Ahn Jong-beom, were key evidence during the earlier trial, and were written down after Park's meeting with Lee, who was not present at the meeting. Prosecutors, citing an earlier North Korean spy case where memos in a computer were deemed admissible, said the memos were admissible, while the defence said they amounted to hearsay.
The defence also argued that there was no direct link between Park and Lee, while Choi was a civilian that had no authority over government decisions.
Jae-yong has been the de facto boss of Samsung since his father and chairman Lee Kun-hee was hospitalized after a heart attack in 2014.
His absence delayed the annual executive reshuffle at Samsung Electronics by six months.
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