He was punished with death on the false charge of "rebellion and spying" 52 years ago.
The retrial proved the illegal investigation of him conducted by the army secret service agency which had no right to inquiry at that time.
The then dictator Syngman Rhee, much upset by the growing public support for him who stood for peaceful reunification, executed him as a "spy" in July, 1959.

On a separate note-

Civic and social bodies and political parties of south Korea held a ceremony in Seoul on Jan. 17 to declare a week of mourning those Ryongsan evacuees killed by the police indiscriminate crackdown.
They included the Korean Confederation of Trade Union, the Society for the Human Rights Movement, the Committee for Probing the Truth about the Ryongsan Tragedy, the Union of Evacuees and the Democratic Labor Party.
The speakers there said that although it is two years since the occurrence of the tragedy, the truth about the mass-killing is not yet probed and the evacuees are still undergoing pain behind bars for the mere reason that they struggled in demand of their vital rights.
Recalling that people in Ryongsan are forcibly evacuated due to the reckless redevelopment policy of the authorities and they are left without any shelter, they declared that this bespeaks that the second Ryongsan tragedy may take place.
They called on the people of various circles to get united to settle the issue of the Ryongsan tragedy and launch dynamic actions to force the authorities to roll back their redevelopment policy.
Earlier, the all-people committee for memorial service for the victims of the Ryongsan tragedy was formed. It groups 106 political parties and organizations and individual personages.