Updated

The Arizona Supreme Court on Tuesday threw out the death sentences of a Tucson man who bludgeoned his girlfriend and her two children to death in 1984 after lying in wait for each of them, ruling that the murders weren't especially heinous even though they were "atrocious" and "senseless."

The state's highest court unanimously vacated two death sentences for James Granvil Wallace, 61, and imposed two sentences of life in prison for the children's killings. That's on top of the life sentence he's already serving for killing his girlfriend, Susan Insalaco.

While the justices wrote that the Feb. 1, 1984, murders of Insalaco, her 12-year-old son, Gabriel, and her 16-year-old daughter, Anna, in their Tucson apartment were heinous in layman's terms, they weren't according to the letter of the law.

That's because the justices found that Wallace didn't knowingly inflict more wounds on the family than he thought were necessary to kill them.

Wallace was living with Insalaco and the children when he came home drunk Jan. 31, 1984, and she told him that he needed to move out, according to court records.

The next day, Insalaco went to work and the kids went to school. Wallace attacked each of them when they arrived home separately after hiding behind the front door.

When Anna came home, court records say that Wallace attacked her from behind and slammed a baseball bat into her head at least 10 times, so hard that the bat broke. Even so, Anna lay moaning and still alive, so Wallace told police that he dragged her into the bathroom and rammed the broken bat into her neck, down her chest cavity and out her back.

When Gabriel arrived home shortly after, Wallace used an 18-inch pipe wrench to bludgeon him about 10 times, crushing his skull.

And when Insalaco got home a couple hours after that, Wallace used the same pipe wrench to hit her in the head four or five times, killing her.

Wallace turned himself in to police the next day and described the killings in detail, although he couldn't explain why he murdered the family

"I thought (Anna) would die with one blow -- that'd be it, like in the movies," Wallace told police. "It ain't that way. She looked me in the eye, she knew who was killing her. ... I wanted to put her out of her misery, man."

Wallace said he used the pipe wrench to kill Gabriel and Insalaco after the bat failed to kill Anna quickly because he didn't want to prolong their suffering.

"Even among capital cases, this case is atrocious," the justices wrote Tuesday. "Wallace's premeditated, brutal murders of Anna and Gabriel clearly were senseless, and the unsuspecting, defenseless victims were helpless."

But the justices said the case falls short of meeting the legal requirement for being especially heinous and, therefore, eligible for the death penalty.

In order to be especially heinous, prosecutors must prove that a killer relished in a crime, inflicted gratuitous violence or needlessly mutilated a victim. They could also argue that a crime was particularly senseless or victims were particularly helpless.

In Wallace's case, prosecutors only argued that he inflicted gratuitous violence. The justices disagreed, saying that every wound Wallace inflicted was meant to cause death because he didn't think he had yet inflicted a fatal wound.

The justices also pointed out that under current Arizona statutes, Wallace most certainly would be eligible for the death penalty.

For example, current statutes allow for a killer to be sentenced to death if he or she killed more than one person at a time. Because Wallace killed Insalaco and her children well before that statute was established, it does not apply to him.

Wallace's Tucson attorney, Carla Ray, told The Associated Press that her client was stunned to learn of the court's decision.

"He's been on death row for 28 years," she said. "In his mind he thought he deserved (the death penalty). He understands it mentally, but emotionally he's having a hard time with it. He knows what he did was wrong."

Ray said that Wallace still can't explain why he killed Insalaco and her children and is nothing but sorry about it.

"He always brings up his remorse and how he just can't wrap his mind around how he was capable of doing such a thing," she said. "He punishes himself more than anyone else ever could."