Serial killer Lee Chun-jae, who is already serving a life sentence for murdering his sister-in-law, appeared in court on Monday to confess to other unsolved murders.

Lee was testifying at the retrial of a man, identified only as Yoon, who was falsely convicted of a crime Lee committed. He appeared in court in prison garb, sneakers and face mask. He was slim and had salt-and-pepper hair.

When Yoon's lawyer asked Lee if he was the culprit behind the serial murders in Hwaseong, Gyeonggi Province that terrified the entire country in the 1980, he responded, "That's right."

Lee was imprisoned for life after raping and murdering his sister-in-law in 1994. He was identified in the Hwaseong murders after police reopened the investigation and matched his DNA to traces found at the crime scenes. He admitted to 14 murders and the rape of over 30 women. But the statute of limitations on his crimes expired in 2006.

Yoon had been convicted of raping and killing a 13-year-old girl in Hwaseong in September of 1988. He was arrested the following year and was given a life sentence. He was freed last year after 20 years behind bars when Lee confessed but filed for a retrial after his release to clear his name.

When asked why he committed the serial murders, Lee said he could not give a clear answer, but explained that he was like a "moth drawn to the flame." He added that he never thought about the suffering of the victims' families but committed his crimes on the spur of the moment.

He said he watched Bong Joon-ho's 2003 film "Memories of Murder," which fictionalizes the Hwaseong killings, but it did not evoke any emotions inside him.

"I repent sincerely for Yoon's wrongful imprisonment for something I did," he said. "I pray that those who died because of me can rest in peace and apologize to their families and others who were affected by the incidents."