South Korean prosecutors on Wednesday arrested Ko Young-tae, a whistleblower in the corruption scandal involving former President Park Geun-hye and her friend Choi Soon-sil.

Ko, who was once a close associate of Choi, is accused of receiving kickbacks in return for wielding influence on personnel appointment at the nation’s customs agency.

He was taken into custody at the Seoul Central District Prosecutors’ Office on Tuesday evening after the court issued a warrant Monday. Prosecutors can hold him for up to 48 hours.

Ko cried foul, calling for the Seoul Central District Court to review the legitimacy of his arrest. He was adjusting the schedule with the prosecution to turn up for questioning when the arrest was made, his associates and lawyers said. The closed-door court hearing is to be held at 2 p.m. Thursday.

“Ko cut off contact with us and went into hiding since last week. So the arrest warrant was issued Monday,” an official from the prosecution told reporters, defying claims from Ko’s lawyers.

Ko offered key testimony about Choi’s close relationship with Park and her meddling in state affairs, which triggered the scandal that eventually forced Park out of office.

While some hailed him as a whistleblower, the lawyers for Choi and Park, as well as the ousted president’s loyal supporters, have denounced Ko as a conman who attempted to capitalize on the Park-Choi relationship. After that fell through, Ko turned to the media seeking revenge, they said.

Ko is suspected of using his close ties to Choi to receive some 20 million won ($17,600) from an official at Korea Customs Service’s Incheon office in exchange for peddling influence to promote the official’s acquaintance to the top post, the prosecution said.

In one of the 2,000 voice recordings unveiled during the trial of Choi, Ko was heard saying to his acquaintance: “I spent money to promote the official to the chief post. I am not trying to earn money, but just to get back the money I spent. There will be a call soon.”

Ko, who served as a director at Choi’s paper company The Blue-K, was among the first whistleblowers to reveal that Choi had access to Park’s presidential speeches and had edited them. He also claimed that Choi had been behind illicit fundraising from local firms.

He has since been summoned for questioning by the prosecution and took the witness stand during Park’s impeachment trial and Choi’s criminal trial. Choi is on trial on charges of extorting donations from local firms for the Mir and K-Sports foundations.

Ko has also been called Choi’s “boy toy” by supporters of Park and Choi, who have said the scandal was sparked by Choi’s adulterous affair with the 40-year-old former fencing champion.

He has denied the rumors, saying he first met Choi through his company, to provide bags and clothing items to the ex-president.

A day after Ko’s arrest, the Seoul Central District Court rejected an arrest warrant for Woo Byung-woo, the former presidential aide for civil affairs, for a second time Thursday, citing the charges against him were “debatable.”

Woo, formally a prosecutor, is suspected of abetting or condoning Choi’s meddling in state affairs and exerting undue influence over the government’s personnel management and the prosecution to sway investigations in favor of former President Park.

The court’s decision not to arrest Woo, one of few people who have avoided legal action in connection with the scandal, drew criticism from the public and opposition lawmakers. They took issue with the prosecution’s purportedly slipshod investigation.

“I don’t think our investigation into Woo was poor. It is a shame that the warrant was rejected, but that’s the court’s decision. We did our best,” an official from the prosecution said.

The prosecution said it will review whether to seek an arrest warrant for Woo again.

By Ock Hyun-ju (laeticia.ock@heraldcorp.com)