A murder defendant who was 16 years old when he repeatedly stabbed his adoptive mother as she lay in bed pleaded guilty in state court Monday to manslaughter.

Ka‘ano‘i Iz Kipapa, 21, faces a maximum 20-year prison term at sentencing in May. He would have faced a mandatory life prison term if he had been found guilty of murder.

According to his plea deal, Kipapa will be free to ask for a reduced eight-year sentence afforded to first-time offenders younger than 22 and will get credit for the time he has been in custody since his arrest in 2014. The state will ask for the maximum 20-year term.

Police said Kipapa stabbed Jolyn Sakae Kipapa multiple times in the head and body July 5, 2014, stopped to call 911 to report that he may have killed his mother, then resumed the attack after he hung up. Jolyn Kipapa was bed-bound because of a leg injury.

The incident happened in the family home in Waim­analo Bay Beach Park. Ka‘ano‘i Kipapa’s adoptive father was the park’s caretaker.

The State Family Court had jurisdiction over the case because Kipapa was a juvenile at the time of the fatal attack. A Family Court judge waived the court’s jurisdiction in October 2014, allowing prosecutors to charge Kipapa as an adult. Another judge ordered Kipapa to remain in custody at a juvenile detention facility until he turned 18. He remains in custody in lieu of $250,000 bail.

The case dragged on as Kipapa underwent mental fitness examinations, neuropsychological evaluation and cognitive testing. There was further delay as his lawyer requested Family Court records. The case moved several times as judges assigned to it retired.

The case was scheduled for a bench trial next month with Kipapa hoping for an insanity acquittal. But that judge later recused himself. Monday’s plea came after Kipapa last week accepted the state’s latest plea offer.