She's one of only six women on death row in the US state of Texas, and Darlie Routier insists she has been wrongfully imprisoned for more than 20 years, accused of killing her two sons.

Routier, 49, was convicted of the 1996 murder of her five-year-old son Damon, who was stabbed to death with his brother Devon, 6, in the family's Dallas home (she wasn't tried for Devon's death — prosecutors wanted a second chance to convict her if the first case failed).

Despite being found guilty of Damon's murder by a jury, Routier has always maintained her innocence — the mother-of-three claiming an intruder broke into the home she shared with her husband and kids and killed the boys, stabbing her several times before she chased him off, reports news.com.au.

Routier will again insist she was wrongfully convicted in a documentary airing this week on American program 20/20, which examines new tests of crucial crime scene evidence.

Advertisement

In a preview of the show, an aged Routier says from Gatesville Prison in Texas: "I cannot actually believe they're doing this to me when I didn't do this. I didn't kill Devon and Damon."

The silly string scene

In a scenario reminiscent of the criticism of Australian woman Lindy Chamberlain, who was accused of not looking "sad" enough over the death of baby daughter Azaria, Routier's behaviour at her sons' graves a week after they died may have turned the public against her.

On what would have been Devon's seventh birthday, Routier and some family members held a grave-side "birthday party".

Footage broadcast on local TV stations showed balloons, Happy Birthday being sung and Routier smiling, laughing and spraying Silly String on the graves.

Family members later pointed out that no footage was aired of a solemn ceremony held moments earlier. But the image of a laughing Routier at her sons' graves is widely considered to have put her in an unfavourable light.

She was arrested and charged with capital murder four days later.

The footage was shown to the jury during the trial.

The night of the murders

At 2.31am on June 6, 1996, Routier called 911. In audio of the call heard in the documentary, she screams "Somebody came in here … they just stabbed me and my children!"

Advertisement

Routier's husband Darian and their infant son Drake were asleep upstairs and unharmed.

Police who responded to the call found Damon and Devon suffering from multiple stab wounds, and they were soon pronounced dead.

Routier suffered stab wounds, which she claims she received chasing off the intruder. Although described as "superficial", one came within two millimetres of her carotid artery. An expert witness during the trial said this would be unusual for a self-inflicted wound.

Routier told police a man wearing dark clothes and a baseball cap attacked them before escaping through the garage.

But investigators said evidence at the scene contradicted Routier's account.

As the Dallas News reported:

Investigators found no blood in the garage or on the garage window or wooden fence surrounding the backyard. The window sills in the garage had layers of dust, and the mulch in the flower beds between the garage and the backyard gate was undisturbed. Lab tests did find fingerprints on the garage window that did not belong to Routier, her husband or law enforcement, but it's unclear who left them. Routier said she found the knife on the floor in the utility room, but investigators didn't find any blood splatter or other marks that would have indicated the knife was dropped there. Blood was found near the kitchen sink but no appreciable amount on the couch where Routier said she had been stabbed. There had been attempts to clean the countertop and sink before police arrived, and police suggested that she may have inflicted the wounds herself, the affidavit stated. Police said a bloody sock was found on the grass several houses down. Routier's relatives cited it as evidence that someone else killed the boys, and the defence said there was no way Routier would have had time to stage the crime scene. Much debate also centred around a bloody fingerprint on the coffee table near her son's body. Part of her appeal centred on the print belonging to an adult, not one of Routier's slain children.

Routier has always maintained a man broke into the house and stabbed her and two of her children before she chased him away. Photo / ABC
Routier has always maintained a man broke into the house and stabbed her and two of her children before she chased him away. Photo / ABC

At the trial, the prosecution claimed Routier murdered her children because of financial problems and described her as a "pampered, materialistic woman with substantial debt, plummeting credit ratings and little money in the bank who feared that her lavish lifestyle was about to end".

Routier's defence team argued there were countless mistakes made at the crime scene and throughout the investigation. An appeals court dismissed these claims, however in 2008 a request for new DNA tests of the evidence was granted. The results of the tests will be explored in the 20/20 documentary.

The Routiers divorced in 2011. Darian has always maintained he believes Darlie is innocent.