The south Korean Central Intelligence Agency arrested Ko when he visited Jeju Island, his birthplace in 1974, and put him to torture and threatened him to wrest from him false confession that he gathered secrets and handed them over to the General Association of Korean Residents in Japan.

After faking up the spying case, the south Korean puppet regime indicted him on charge of the violation of the "Security Law" and sentenced him to ten years in prison and ten years of suspension of qualifications.

In this regard the victim demanded the court retry the case in 2011.

The court declared him not guilty after recognizing that he was illegally arrested and investigated and the case was based on a false confession.