A US former policeman dubbed the "Golden State Killer" was sentenced to life in prison without the possibility of parole Friday, as he finally apologized to his victims for a brutal decade-long crime spree that terrorized California.

Joseph James DeAngelo Jr -- who had already confessed to 13 murders and dozens of rapes in the 1970s and 1980s under a deal to avoid the death penalty -- sat impassively behind a face mask in the Sacramento courtroom for a fourth consecutive day as his sadistic crimes were listed.

"The survivors have spoken clearly. The defendant deserves no mercy," said Judge Michael Bowman, to thunderous applause from victims and their families.

He handed down the "absolute maximum sentence the court is able to impose under the law."

Moments before he was sentenced, DeAngelo stood and apologized to those in attendance.

"I've listened to all of your statements. Each one of them. And I'm truly sorry to everyone I've hurt," said DeAngelo.

DeAngelo, 74, was ordered to serve 11 consecutive life terms without parole for 13 first-degree murders. The first three murders took place before a 1979 legal change, and those sentences are served concurrently.

The convicted killer, who has three adult daughters and grandchildren, was not arrested until 2018, three decades after the "Golden State Killer" had last struck. 

The manhunt finally ended after investigators successfully matched DNA from crime scenes with a family genealogy database used by his relatives.

DeAngelo's known attacks began in 1975, initially in the Sacramento area of central California, before spreading out across the state.

He repeatedly broke into homes under cover of darkness to rape women and girls, and murdered many victims in their beds.

Prosecutor Todd Spitzer told the court he wished DeAngelo had received the death penalty.

"Instead of (you) just staring straight forward in some glazed-over eyes, I wanted to stare at you, watch you, silently slip into the night," Spitzer said to DeAngelo.

"But we met with our victims. We knew the age of the case. We knew how long it took to solve. And we knew that this was the right thing to do -- so you could all be here today in your lifetime," he told the victims and families.

DeAngelo's spree apparently ended abruptly in 1986 with the rape and murder of an 18-year-old girl.

Along the way, the meticulous masked assailant was given a number of other nicknames including the East Area Rapist, the Diamond-Knot Killer and the Original Nightstalker.

- 'The boogeyman' -

His sentencing followed three days of emotional testimonies from some of the victims and family members, who described in graphic detail the devastating impact DeAngelo's crimes had wrought on their lives.

Patricia Murphy, who was 29 and a mother of two when DeAngelo repeatedly raped her in her parents' home in September 1976, called DeAngelo "an evil monster with no soul" in a statement.

"May you rot in prison," said her daughter Patti Cosper, who raised her middle finger, pointing it at DeAngelo, as she read out her mother's statement. 

Moments before he was sentenced Friday, DeAngelo's lawyers attempted to paint a picture of their client as a family man, and said that "we hope that by admitting these offences, Mr DeAngelo has provided some peace to their survivors and their loved ones."

A statement read out from DeAngelo's sister blamed their father "in part" for "mental and physical abuse" but insisted she was not "searching for an excuse for it all."

A frail-looking DeAngelo was wheeled into the room Friday wearing an off-white sweatshirt over his orange prison jumpsuit.

Following the sentencing, prosecutors showed journalists video footage of DeAngelo walking easily around his prison cell, accusing him of faking his own feeble health in a bid for sympathy.

"It was all BS," said Spitzer, of DeAngelo's courtroom apology. 

DeAngelo also pled guilty on 13 kidnappings for robbery charges. He was ordered to serve an additional life sentence for one of those counts that took place after the January 1979 legal change.

Finally, DeAngelo was sentenced to eight years in prison on weapons charges.

Prosecutor Diana Becton called DeAngelo "the boogeyman, the man whose horrific unspeakable crimes devastated the lives of so many people, lives that will never be the same, lives forever changed, moments, hours of terror that can never be erased or forgotten."

"After today's sentencing Mr DeAngelo will never threaten our victims again," she added. "He will never harm another soul."