Koh Yu-jeong, who is suspected of murdering her former husband, has sued her current spouse for defamation.

Chungbuk Provincial Police Agency said Monday that Koh has filed defamation charges against her husband, who alleges that she is responsible for the death of his 4-year-old son.

He also accused police of “lax investigation” via an online petition posted July 29 on Cheong Wa Dae’s website.

His son -- Koh’s stepson -- died March 2 at the couple’s home in Cheongju, North Chungcheong Province. In the ensuing investigation, Koh’s husband told police he found the child dead next to him when he woke up in the morning while Koh slept in another room.

Although the National Forensic Service’s autopsy revealed the child likely died from suffocation, police viewed the case as possible murder and booked the couple in early July. The charge was later changed to accidental homicide.

Koh accuses her husband of making her out to be a killer of her stepson, police said.

Police are conducting forensic profiling of the couple.

On June 1, Koh was arrested as a key suspect in the death of her ex-husband, identified only by his surname Kang. Police suspect Kang was murdered May 25 at a vacation home the divorced couple had rented. Koh’s first trial was held Monday.

By Kim Arin (arin@heraldcorp.com)