The top court on Thursday sent the bribery case of former Vice Justice Minister Kim Hak-ui back to a lower court for a retrial, calling into question the reliability of testimony used against him.

The Supreme Court said it "cannot rule out the possibility" that a key witness could have changed his testimony that led to Kim's conviction, because of appeasement or pressure from the prosecution.

The court said the prosecutors should "prove" that there were no such illegal actions based on documents that recorded the process of questioning and investigation.

The witness, a businessman surnamed Choi, initially denied bribing Kim but changed his position after being grilled by investigators.

The court also allowed Kim to be freed on bail, eight months after he was arrested in court on bribery charges.

Later in the afternoon, Kim was released from the Seoul Detention Center in Uiwang, south of Seoul. He did not respond to questions from reporters and got onto a sedan waiting for him outside the prison.

In October, an appellate court reversed a previous non-guilty verdict and sentenced Kim to 2 1/2 years in prison for taking about 43 million won ($38,533) in bribes from Choi between 2000 and 2011.

It, however, acquitted him of receiving bribes and escort services between 2006 and 2008 from Yoon Jung-cheon, a jailed construction contractor and a key figure in Kim's high-profile sex scandal. The top court on Thursday upheld the acquittal, citing lack of evidence and the expiration of the statutes of limitations.

The scandal became publicly known after a video clip was leaked in 2013 showing a group of men, including one believed to be Kim, having a sex party with about 30 women in a remote villa owned by Yoon. Yoon was later convicted only on fraud charges because the statute of limitations for his sexual offenses expired.

In 2013 and 2014, Kim was probed by the prosecution and police over various suspicions, but he was cleared of all charges due to lack of evidence. The special team of prosecutors resumed the probe in March 2019, following an order from President Moon Jae-in.

Kim was indicted in June 2019 on charges of receiving bribes and sexual favors. He was cleared of all charges by a district court, but an appellate court found him partially guilty of bribery.

He is also at the center of another controversial case in which the Ministry of Justice allegedly enforced an illegal exit ban in March 2019 to stop him from leaving the country.

Last month, Lee Sung-yoon, chief of the Seoul High Prosecutors Office, was indicted over allegations that he exercised undue influence in 2019 to block an investigation into officials involved in the exit ban. (Yonhap)