A death penalty trial, which would follow a lengthy preliminary hearing in May, could cost taxpayers an estimated £15.5 million.

The Sacramento County public defender’s office, which represents DeAngelo, has quietly canvassed families of the victims to test their willingness to accept a plea deal.

Suspect serial killer DeAngelo has been charged with 13 counts of murder as well as multiple kidnapping and weapons charges.

The former police officer was arrested on the outskirts of Sacramento, California, in April 2018.

The investigation was the first high-profile case to be cracked with genetic genealogy.

The technique relies on identifying crime-scene DNA with that of family members in genealogy databases.

The people who submit DNA samples typically do so to research their family history.

Many have been surprised to learn that their genetic profiles have been used to help solve crimes.

DeAngelo’s arrest has since led to dozens of other US law enforcement agencies to begin solving long-unsolved violent crimes.

The technique has generated a backlash from some genealogists, privacy advocates and legal scholars who are worried the police and the FBI are abusing such databases.

The Golden State Killer had remained one of America’s biggest and most heinous unsolved crimes for the past 40 years

DeAngelo has been linked to 13 murders, 45 sexual assaults and more than 120 burglaries from Sacramento to Southern California’s Orange County from 1976 to 1986.

The victims ranged in age from 13 to 41 and included women at home alone or with their children or husbands.

Following his arrest, Jane Carson Sandler, who survived a sexual assault by the murderer, said: “I am speechless. Almost sick to my stomach because I am so excited. It is a dream come true.”

The attacks began in Sacramento in 1976 with the June 18 rape of a woman in the Rancho Cordova-Carmichael neighbourhood.

The attacker wore a ski mask and would prise open windows and doors of homes of single women or couples.

Once inside, he would enter the bedroom and shine a torch into his victims’ eyes.

In 2016, authorities began publicising the search nationally in advance of the 40th anniversary of his first attack.

“The answer is out there somewhere,” Sacramento District Attorney Anne Marie Schubert said at the time.

“It is a case that needs to be solved because these women and these families deserve the answers and the person if alive needs to be brought to justice.

“It has been 40 years of this.”