The man known as the Golden State Killer will finally admit to the horrific crimes he committed in the '70s and '80s ... including 13 first-degree murder charges he's facing.
Joseph James DeAngelo Jr. is appearing in a makeshift courtroom Monday -- onstage in a ballroom at Cal State Sacramento -- where he will plead guilty to the 13 counts of murder and 13 counts of kidnapping for purposes of robbery.
DeAngelo's also expected to admit guilt to 62 other rapes and abductions during the plea hearing ... crimes for which the statute of limitations expired long ago.
Sacramento County Deputy D.A. Amy Holliday says prosecutors agreed not to seek the death penalty and expect DeAngelo to be sentenced to life without parole.
The 74-year-old former police officer's guilty plea comes after decades of mystery over the rapes and killings at his hands, which took place between 1973 and 1986.
DeAngelo's trail of terror led to monikers like the "Visalia Ransacker," "East Area Rapist," "Original Night Stalker" and finally, the "Golden State Killer," and left "communities terrified for years" ... according to prosecutor Thien Ho at Monday's hearing.
After more than a 40-year hunt, DeAngelo was arrested on April 24, 2018 after being ID'd by crime-scene DNA.
The Golden State Killer's crimes and investigation are the subject of the new HBO documentary, "I'll Be Gone in the Dark," which highlights the late Michelle McNamara's mission to crack the case and find him