A jury in Idaho has unanimously agreed that “doomsday prophet’ Chad Daybell deserves the death penalty for the murders of his wife and his girlfriend’s two youngest children.

The 55-year-old showed no emotion as he was told he would face the death penalty for the murders of Tammy Daybell, 16-year-old Tylee Ryan and seven-year-old Joshua “JJ” Vallow.

The mother of the children is Lori Vallow Daybell, whom Chad Daybell married shortly after his wife’s death.

Vallow Daybell was convicted last year of the three murders and is now awaiting trial in Arizona, charged with murder in connection with the fatal shooting of her fourth husband, Charles Vallow, who was JJ’s father.

The case began in 2019, when a family member called police. Investigators soon realised both children were missing and a multi-state search ensued.

Nearly a year later, their remains were found buried on Chad Daybell’s property. Tylee’s DNA was later found on a pickaxe and shovel in a shed on the property while JJ’s body was wrapped in rubbish bags and duct tape, prosecutors said.

During a nearly two-month trial, prosecutors said Chad Daybell, a self-published author who wrote doomsday-laced fiction, promoted unusual spiritual beliefs including apocalyptic prophecies and tales of possession by evil spirits in order to justify the killings.

Daybell’s defence attorney John Prior argued during the trial that there was not enough evidence to tie Daybell to the killings, and suggested Vallow Daybell’s older brother Alex Cox was the culprit.

Mr Cox died in late 2019 and was never charged. Vallow Daybell was convicted last year and sentenced to life in prison without parole.

During the sentencing hearing, Mr Prior asked the jurors to judge Daybell on his life before he met Vallow Daybell, describing her as a bomb that blew him off the trajectory of an otherwise wholesome life.

But Daybell also declined to offer any mitigating evidence during the sentencing hearing.

Mitigating evidence is often used to encourage jurors to have sympathy for a defendant in an effort to show that a life sentence would be more appropriate than capital punishment.

Family members of the victims gave emotional statements to the jurors.

JJ Vallow’s grandmother Kay Woodcock tearfully described how the seven-year-old would show empathy and compassion to others through soft touches and by frequently asking if those around him were OK.

She also said Tylee was a doting big sister, and that it warmed her heart to see them together.

“I can’t express just how much I wish for more time to create memories,” Ms Woodcock said, beginning to weep.

Vallow Daybell’s oldest child Colby Ryan described what it was like to lose his entire family. His father died years earlier.

“My three kids will never know the kindness of Tylee’s heart or JJ’s silly and goofy personality… The only way I could describe the impact of their lives being lost is like a nuclear bomb dropping,” he said. “It’s not an overstatement to say that I lost everything.”

To impose the death penalty, the jurors had to unanimously find that Daybell met at least one of the “aggravating circumstances” that state law says qualifies someone for capital punishment.

They also had to agree that those aggravating factors were not outweighed by any mitigating factors that might have lessened his culpability or justified a lesser sentence.

Idaho law allows for execution by lethal injection or firing squad, though firing squad executions have never been used in the state.