WARNING: This story contains graphic details

HALIFAX — A Nova Scotia couple has been sentenced to life in prison for the killing and horrific dismemberment of a young Halifax mother who pleaded with them to spare her life.

Jason James Johnson and Kelly Amanda MacDonald, who are both in their 30s, pleaded guilty Thursday to second-degree murder and interfering with human remains in the death of Catie Miller, 29.

“She pleaded for her life but you ignored her pleas,” Justice Patrick Duncan told them as he ruled Johnson would be eligible for parole in 20 years, and MacDonald in 16 years.

The judge called it a “cold and heinous crime,” and said both killers had the “sole focus of silencing her forever and then taking extreme steps to try and hide the body and your responsibility.”

Johnson had previously been in a relationship with Miller, according to prosecutor Robert Kennedy.

In an agreed statement of facts read by Kennedy, the Nova Scotia Supreme Court heard that Johnson was arrested on Nov. 22, 2014, out of mounting concerns that he would “follow through on fantasies to kill again.”

The statement said that on July 15, 2014, Johnson beat Miller with a tire iron and confined her in the trunk of his Pontiac Grand Prix.

He met MacDonald in Enfield, N.S., and with their child in the back seat, they drove to Lawrencetown, where they lived, as Miller awoke and screamed, “Jason you don’t have to do this!”

The court heard that MacDonald told Johnson to “finish her off.”

At one point, he stopped and cut her throat with a hooked knife MacDonald had obtained. The prosecutor said when Miller continued to make noise in the trunk, MacDonald again urged her common-law partner to “finish it,” and he opened the trunk and slit Miller’s throat a second time.

The pair went to another residence in Sheet Harbour late that night, where tarps and tools were laid out on the lawn.

Johnson used an axe and hand saw to remove Miller’s head and hands, “to prevent her identification through dental and fingerprint records,” according to the agreed statement of facts.

The prosecutor said outside court that he couldn’t comment on the possible motive for the original beating, other than to say that Johnson and Miller had a “prior domestic relationship,” and that Johnson’s assault on Miller started “on the side of a road” in Halifax on the same day as her murder.

Catie’s mother, Terry Miller, spoke in court as two photographs of her daughter were held nearby her.

“I must face a life where I will always grieve my daughter... my dreams for her have vanished. I’m left with endless pain,” she said.

“Evil visited our family... I’m continuously asking ’why, why, why?”’

Catie, who had a young son, was last in contact with her family on the day of her death, and was reported missing a few days later.

Months later, MacDonald took undercover officers to the location where Miller’s torso was hidden in Lawrencetown, tied to a tree.

The victim’s father, John Miller, says his grandson will need “emotional and financial support.”

“There’s no reason for the viciousness and disrespect, there’s no reason,” he said, weeping in court.

Johnson declined to make any comment to the court. MacDonald spoke briefly, offering an apology to Catie’s father and son.

“I’m very sorry to John ...in the death of Catie, a young mother and daughter,” she said.

“There are no words that I can say for either of you to forgive me for taking Catie’s life. I just hope that one day that God chooses to forgive me on your behalf.”