Darlie Routier's sons were stabbed by an intruder. Days later, she was arrested.

At 2.31am on June 6, 1996 emergency dispatchers received a frantic call.

“Somebody came in here,” a woman screamed down the line. “They just stabbed me and my children.”

Darlie Routier, then 26, described how an intruder had stabbed her and her young sons, six-year-old Devon and five-year-old Damon.

Within minutes, police arrived at the house in Dallas, Texas and found the boys suffering from multiple stab wounds – they were soon pronounced dead.

Routier also suffered “superficial” stab wounds, which she claimed she received when she chased off the intruder. One wound came within two millimetres of her carotid artery in her neck.

Her husband Darin and their youngest son, seven-month-old Drake, were asleep upstairs at the time and both escaped harm.

Routier described the intruder to police: A man wearing dark clothing and a baseball cap.

He had escaped through the garage, she said.

But scene investigators had their doubts. Dallas News reported they found no blood in the garage, and although a window screen in the garage had been cut open, the window sills in the garage had layers of dust.

Lab tests found fingerprints on the garage window that did not belong to Routier, her husband or law enforcement, but it's unclear who left them.

There was no blood splattered in the utility room, where Routier said she found the knife that was used, and no significant amount on the couch where she claimed to have been stabbed.

Much debate also focused on a bloody fingerprint found on the coffee table near one of the boy's bodies which belonged to an adult, not one of her children.

Then, just eight days after her son's deaths, public opinion turned on Routier - echoing the criticism of Australian Lindy Chamberlain, who was accused of not grieving enough over the death of her baby daughter Azaria and was wrongfully convicted over her death.

On what would have been Devon's seventh birthday, Routier and her family held a birthday party at her son's grave.

Footage from the 'party' showed Routier laughing, smiling and spraying silly string.

Family members pointed out that no footage from an earlier solemn ceremony was aired, but the image of Routier laughing was enough to damage her public reputation.

Just four days later she was arrested and charged with murder.

The birthday party footage was shown during her trial.

A mother on Death Row for the unthinkable.

Now, as the court orders new testing on crucial crime scene evidence – what will happen next to Darlie Routier?

See the exclusive interviews and stunning details – on the 20/20 Documentary Event Special – Friday Night at 9|8c on ABC. pic.twitter.com/vIs0sOzTnF

— 20/20 (@ABC2020) May 6, 2019

At trial, prosecutors argued that Routier had killed her children due to financial difficulties. Prosecutors described her as a materialistic woman with mounting debt who feared her "lavish lifestyle was about to end".

Her defence attorneys claimed there were many mistakes made at the crime scene and throughout the investigation into Routier. They argued there was no motive for Routier to kill her children.

It took the jury 10 hours spread over two days to convict Routier of capital murder of Damon - she was not tried for Devon's death as prosecutors wanted to pursue a second indictment if the first case failed.

Routier, now 48, has been on death row in Texas' Gatesville Prison for more than 20 years and has always maintained her innocence.

She will lay bare her first person account of the horrific 1996 murders in a two-hour program by ABC's 20/20 airing on Friday in the United States, which will examine new tests of crucial crime scene evidence.

"I cannot actually believe they're doing this to me when I didn't do this," Routier is seen saying in the show's preview. "I didn't kill Devon and Damon."

Along with her personal account, the documentary will include the grave site birthday party footage, her current lawyer's theories and an interview with her ex-husband Darin Routier, who has always believed her innocence.