A court in Seoul is set to decide whether the billionaire heir-apparent of the Samsung conglomerate will be jailed for corruption.
Lee Jae-yong is facing accusations of bribery linked to a scandal that triggered the impeachment of South Korea’s former president.
Prosecutors are asking for a 12-year jail sentence. He denies all charges.
The case has gripped the public amid growing anger against South Korea’s biggest companies, known as chaebols.
Mr Lee, also known as Jay Y Lee, has been detained since February on a string of corruption charges including bribery, embezzlement and hiding assets overseas.
He stands accused of giving donations worth 41bn won ($36m; £29m) to non-profit foundations operated by Choi Soon-sil, a friend of South Korea’s former President Park Geun-hye, in return for political favours.
The 49-year-old had been standing in as chairman for his ill father, Lee Kun-hee, who suffered a heart attack and slipped into a coma in 2014.
Prosecutors alleged that the donations were made to Ms Park’s confidante to win government support for a big restructuring of Samsung that would strengthen Mr Lee’s control over Samsung Electronics.
But the defence said he was not involved in making day-to-day business decisions at South Korea’s biggest conglomerate and that the payments were signed off without his knowledge.
The charges carry a maximum sentence of 20 years in prison, but he would almost certainly appeal against any conviction.
Yet he may yet escape a jail term even if he is convicted. Many top executives of South Korea’s biggest companies, including his father, have been convicted of crimes but were pardoned.