Is this Texas mother a victim or a murderer?

The CNN Original Series "Death Row Stories" airs Sundays at 10 p.m. ET/PT.

(CNN)It was a necklace that saved Darlie Routier's life on June 6, 1996.

That night, Routier's throat and arms were slashed, and her two oldest sons -- 6-year-old Devon and 5-year-old Damon -- were brutally stabbed to death in their Rowlett, Texas, home.
By the time the police and paramedics arrived, Devon was already dead. They tried to revive Damon, but he passed away at the scene shortly after.
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Darlie's necklace was so deeply pressed into her throat, it had to be surgically removed. But, it ultimately stopped the knife less than two millimeters away from her carotid artery.
In the recording of her 911 call, Routier frantically described how an intruder came into the home and attacked her and her sons.
"They just stabbed me and my kids ... my little boys," Darlie Routier said to the operator.
She would later testify that, before the attack, she had fallen asleep in front of the television with the two boys. Her husband and infant son, Drake, were asleep upstairs at the time and unharmed.
Twelve days after the murders, Routier was arrested after police found inconsistencies in her story, most pressingly about where she found the knife.
"It was a bloodbath. And when a crime like that happens, it's someone in the house that did this," Toby Shook, the assistant district attorney at the time, told "Death Row Stories."
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The prosecution would later use this as a key piece of evidence against Routier, as well as the fact that valuable jewelry was left on the counter in plain sight and untouched. Prosecutors also pointed out that Routier, at one point in the 911 call, was worried about touching the knife.
"God ... I bet if we could have gotten the prints maybe," she told the 911 operator.
Perhaps the most damning piece of evidence was a video of Routier, just eight days after the attack, smiling, singing "Happy Birthday" and shooting Silly String on her sons' grave site.

The 'Dallas Susan Smith'

Routier was quickly labeled as the "Dallas Susan Smith," according to Kathy Cruz, who wrote the book "Dateline Purgatory: Examining the Case that Sentenced Darlie Routier to Death."
Just a few years prior, Susan Smith had claimed an assailant had taken her two young boys in a carjacking before confessing that she strapped them into their car seats and pushed her car into a lake.
The media circus soon took over.
"I do believe it is very likely that the Susan Smith case played a role in the rush to judgment on Darlie Routier," Cruz wrote in an email to CNN.
After just eight hours of deliberations, the jury found Routier guilty. She was sentenced to death by lethal injection.

Building the appeal

Soon after, appellate attorney Stephen Cooper was assigned to the case and made a shocking discovery: Court reporter Sandra Halsey had made more than 30,000 mistakes in the trial transcript. Forty to 50% of those were "substantial," Kathy Cruz said.
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Without a reliable transcript, Cooper couldn't stage a proper appeal. He felt the substantiated errors would earn Routier a new day in court, yet her motion for a new trial was denied.
Instead, the state offered her life in prison if she dropped her appeal and admitted to her children's murder. Routier refused.
Cooper says he also came across game-changing pieces of evidence that the jury didn't see.
"What was not shown the jury was this two-hour memorial video that took place before the Silly String incident," Cooper said.
Also unseen: photos of Routier's extensive wounds and bruises which, in her attorney's eyes, cast doubt on whether her injuries could have been self-inflicted.
Cooper also questioned why Routier's husband was not investigated more thoroughly. In a signed affadavit, he admitted to one insurance scam as well as a plot for a staged home robbery so he could collect a claim. Darin Routier would have collected on his wife's life insurance had she died of her injuries.
Darin Routier denied involvement in the murders, and subjected himself to a polygraph test by Brian Pardo, a wealthy businessman who had become interested in the case.
He failed.
"Darlie had no motive at all, and Darin had $250,000 worth of motive," Pardo said.

Questioning the timeline

Still, most look at a bloody boy's sock found in an alley 75 yards away from the home as what could ultimately help free Routier.
"That sock is the most important piece of evidence in this entire case," Cruz said.
Cooper argues it's nearly impossible for her to have had enough time to stab the two boys, call 911, cut the screen in her home, run the sock down an alley and come back and inflict her own wounds.

Victim or perpetrator?

Routier asserts her innocence to this day and waits on death row for her appeal to move forward. She and her husband divorced in 2011. Darin Routier currently lives in Lubbock, Texas, with their surviving son, Drake.
Tune in to "Death Row Stories," Sunday at 10 p.m. ET/PT to see all the evidence of the case against Darlie Routier.
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