Mordverdächtiger einer Schülerin aus Gwangju gibt Vorwurf der Vergewaltigung zu

Question

“As he and his lawyer confirmed the footage collected from a car parked near the crime scene, he admitted to the rape-murder charge.
While simple murder under the Criminal Act carries a potential sentence of death, life imprisonment or a fixed term of five years or more, rape-murder falls under the Act on Special Cases Concerning the Punishment of Sexual Crimes, which limits sentencing to either life imprisonment or the death penalty.”

So, starting from the assumption that a death sentence is not gonna happen. Why would this scumbag ever admit the rape-murder charge considering it only makes things worse for him? Is there any potential benefit for him ?