This photo shows Park Ki-rae (second from right) attending a court trial over allegations of spying for North Korea in the early 1970s. (Courtesy of bereaved family members of Park)

The Supreme Court of South Korea cleared a man who served 17 years in prison for allegedly spying for North Korea in 1975 of his charges in a retrial on Thursday.

Seoul's top court upheld an earlier ruling in 2022 that the evidence that originally put Park Ki-rae in jail for his breach of the National Security Act is not admissible, given that the investigative authorities during former President Park Chung-hee's military dictatorship had obtained the evidence and a confession by violating the defendant's human rights, through unlawful detention and torture.

During the military dictatorship, Seoul's anti-communist sentiment had continued to grow, particularly after the North's failed assassination attempt on the president in 1968, partly in order for the then-president to consolidate his control over South Koreans.

Defendant Park, a reunification activist, was one of the people arrested for attempting to rebuild a political party called the Unification Revolutionary Party, which the military junta had cracked down on after the revelation of party members' failed subversive activities against the then President Park in late 1960s.

Prosecutors then indicted him in 1974 for allegedly inviting others to join the party, illegally entering North Korea to communicate with North Koreans, conducting spying activities against Seoul and leaking military information.

Park was sentenced to death in April 1975. However, he ultimately served in total 17 years behind bars as his sentence was commuted several times until he was released on parole in 1991.

He continued his reunification activities after he was released from prison until he passed away in 2012.

This photo shows bereaved family members of the defendant Park Ki-rae, who was acquitted of spying charges in a Supreme Court verdict Thursday following a retrial. (Yonhap)

The defendant's bereaved family members sought a retrial of his case in 2018 in hopes of removing his criminal record, questioning the evidence's admissibility to the court. The retrial of the case began in 2020.

The prosecution, however, continued to seek life imprisonment for him, claiming that his statements to the court had been made with the help of his attorneys.

After the Supreme Court verdict, the defendant's son, Park Chang-seon, told reporters that it was "exceptional and inappropriate for prosecutors to seek life imprisonment to a person who had endured torture and served 17 years of imprisonment unjustly," adding that Park was the first individual to be acquitted of spying accusations related to the Unification Revolutionary Party crackdown in a retrial.