The presidential candidate for the ruling Democratic Party of Korea is facing growing criticism for defending a nephew who brutally killed two women and for later downplaying the case, with the opposition questioning his fitness to hold office.

Lee Jae-myung is a qualified lawyer in South Korea, having passed the bar exam in 1986, and he served as a defense attorney for his nephew when he was accused of murdering his girlfriend and her mother in 2006.

But the fact that Lee defended his nephew in court is not the main focus of the criticism. The candidate has instead been denounced for referring to the murders as an unfortunate case of "dating violence" when apologizing to the victims, despite the brutal nature of the crimes.

Kim Byong-joon -- the top campaign official for the main opposition People Power Party’s presidential nominee, Yoon Seok-youl -- denounced Lee in a press briefing Sunday.

"The murder case he defended was not a usual murder case," Kim said. "It was a grotesque case of (the defendant) stabbing the two people 18 and 19 times each for a total of 37. How can there be a mistake or misstatement in defining the nature of this case?"

On Wednesday, Lee had said in a Facebook post, "One of my family members committed a serious dating violence crime in the past, but his family could not afford an attorney, so I had to provide defense for the case as I was the only attorney among his relatives.

"I hesitated a lot as I already was a politician then, but it was hard to avoid the job."

His comments caused an uproar after it was found that the widely publicized murder case involved Lee's nephew barging into his girlfriend’s home in Gangdong-gu, eastern Seoul, and brutally murdering her and her mother in May 2006.

The Supreme Court upheld a life sentence for Lee's nephew in 2007.

A member of the victims' family criticized Lee and his nephew Friday in an interview with the Munhwa Ilbo newspaper, saying he felt heartbroken hearing Lee refer to the murders as a case of dating violence and that the candidate had never contacted him once to offer an apology or his condolences.

Lee apologized shortly after the interview was published, saying he had never attempted to hide or downplay the case and had used a "clumsy expression."

The presidential candidate has also faced criticism for citing the defendant’s mental illness in appealing for lenience, when he himself has publicly criticized the practice of reducing sentences on health grounds.

"How could an attorney engaging in politics use 'physical and mental illness' as a defense tactic?" Kim from the People Power Party said in the Sunday briefing.

"The difference between a general on a battlefield and a politician is that a general must win but a politician must win in the right way. He is not qualified to serve as a political leader."

The Constitution states that punishment can be mitigated when an offender is unable to exercise good judgment or self-control because of a mental disorder.

Lee and the Democratic Party have not made any official response to the criticism. Past records show that Lee has repeatedly cited mental illness as part of his defense tactics in other criminal trials.

A year after the Gangdong-gu murder case, Lee served as one of two defense attorneys in a murder case in Seongnam, Gyeonggi Province, where a man stabbed his ex-girlfriend eight times and killed her in front of her daughter.

The defendant was sentenced to 15 years in prison and is set to be released in August 2022.

Court records show that Lee argued the defendant was heavily intoxicated during the crime and lacked the ability to make sound judgments. The defendant prepared pesticides and a sashimi knife before committing the murder.

While Lee explained that he had defended his nephew due to their family relationship, local statutes provide for the defense of accused people who can't pay.

Lee's nephew could have obtained a state-appointed attorney as guaranteed under the Constitution, which states that the court can appoint a defense counsel for a criminal defendant if requested "because of poverty or for any other reason."