Killing a mentally ill person is illegal, mainly based on the following:　　According to the Criminal Law　　Article 232　【Intentional Homicide】Whoever intentionally kills another shall be sentenced to death, life imprisonment, or fixed-term imprisonment of not less than ten years; if the circumstances are less serious, the sentence shall be fixed-term imprisonment of not less than three years but not more than ten years. 　　Article 233　【Negligent Homicide】Whoever causes the death of another through negligence shall be sentenced to fixed-term imprisonment of not less than three years but not more than seven years; if the circumstances are less serious, the sentence shall be fixed-term imprisonment of not more than three years. In cases where other provisions are stipulated by this law, those shall be followed.‍