'The Last Defense': An in depth look at the series exploring death-row convictions

Part of the series focuses on Darlie Routier, a woman on death row after being found guilty of killing her two sons.
7:36 | 06/22/18

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Transcript for 'The Last Defense': An in depth look at the series exploring death-row convictions
Reporter: It was a case that both captivated and horrified the nation. A young Texas mother, Darley rutier, sentenced to death after the brutal stabbing murders of her two young sons. Darren believes he's married to an innocent woman. When they were telling me that I had done this, I was in shock. I was completely blind-sided. Just -- I couldn't even grasp what they were telling me. Reporter: She's always maintained her innocence. Now more than 20 years later, the controversial case is the subject of an ABC docu-series "The last defense" from executive producer Viola Davis that explores whether she should have been put on death row in the first place. Her conviction is based on problematic evidence. Reporter: Attorneys Vanessa podkin and Aida lesinring were legal consultants to "The last defense." I know she shouldn't have been proven guilty beyond a reasonable doubt. Reporter: Darren rutier is Darley's ex-husband and father of her children. Darley is 100% innocent. The truth is always going to be there. It's still there now. Reporter: On June 6th, 1996, in a quiet suburb of Dallas, Texas, 26-year-old Darley rutier made a frantic call to police. 911, what is your emergency? Somebody came in here -- they broke in -- Ma'am? They just stabbed me and my children -- What? They just stabbed me and my children, my little boys! Who did? They're dying! I was asleep upstairs. I didn't hear a sound from the boys, I didn't hear a sound from Darley until she started screaming. Reporter: Officers who arrived at the house found a gruesome scene. The two boys, Damon and Devin, stabbed to death. Darley herself had multiple stab wounds but quickly recovered. She had a gash on her arm that cut to the bone. She had a slash across her throat that very narrowly missed her carotid artery. She very nearly died that night. Reporter: Just days later, the grief-stricken couple laid their two boys to rest. Their quiet community gripped with fear. A killer still on the loose. It's scary. To think that, you know -- I don't think they had any suspects yet. When the police were there, they saw a cut screen in the garage. Which seems to indicate that someone cut the screen from the outside, stepped through the screen, into the garage, and headed for the main part of the house. Reporter: After a week-long investigation, police announced their findings. We believe that the white male suspect described by Darley rutier as the man who attacked her and murdered her children never existed. We also believe that the wounds present on Darley rutier were self-inflicted. Reporter: Prosecutors charged her with capital murder, alleging she stabbed herself, Shen staged the crime scene. I remember feeling like, these people are wrongfully trying to accuse me of murdering my children and trying to kill me. I remember just feeling so scared. It couldn't be happening. This just couldn't be happening. Reporter: But at trial, prosecutors presented a relentless case, portraying her as a self absorbed, materialistic woman living in debt, suffering postpartum depression. They introduced her evidence of her going to strip clubs with her girlfriends on mothers day, the fact that she had a sex toy in the house, that she had fake breast implants, that she wore a lot of jewelry -- Reporter: Then the matter of a controversial but crucial piece of blood spatter evidence introduced by an expert for the prosecution. When he testified that that was cast-off blood, that it was consistent with Darley rutier actually taking the murder weapon, striking the boys, and then actually small bits of blood actually came off the blade and landed on the shoulder area. Reporter: Another key moment, prosecution experts testified tiny fibers from the screen in the garage were found on a knife found inside their own kitchen. That piece of evidence is devastating to the defense. Because it shows that someone inside that house cut open the screen. How in the world else could a fiber from that screen in the garage get on a bread knife in the kitchen? Reporter: Perhaps the most damning piece of evidence of all was her own behavior eight days after the murders, captured by a local TV station. ??? Happy birthday to you ??? For some, this may seem a strange thing to do in an odd place and time. ??? Happy birthday dear Devin ??? Singing happy birthday in a cemetery to a son who was brutally stabbed to death just over a week ago. I love you, Devin and Damon! Davis plays that video for the jury saying, here's a come who lost her children and literally dancing on the graves. They only showed a little clip of that. He didn't see what came before, they didn't see what came after. They reached a verdict, we're waiting to get into the courtroom to find out what it is. All 12 jurors raised their hand when asked by the judge if she should get the death penalty for murdering her sons. Reporter: Darley rutier found guilty and sentenced to death. She's not so much doting on her kids as doting on herself. Reporter: Juror Paris recalls the evidence that sealed her fate. There's many ways to mourn the loss of a children or parent. But having a birthday party and throwing silly string around in a graveyard? Uh-uh. I lovedeing a mother. I loved Devin and Damon. The idea that I would want to murder my children -- it was just so ridiculous. Reporter: 20 years after her conviction, her attorneys want the evidence that put her on death row to be reexamined, including a fingerprint on a living room table imprinted in blood that has never been entered into the federal database. Could be the print of the person who actually did this. Any chance in your minds her conviction might be overturned? Absolutely. First and foremost, the state used blood splatter analysis to convict her. And what we've learned in the 20 years since her trial is that blood spatter analysis is highly subjective. Reporter: For now, rutier has no execution date scheduled. To give you some idea, there's been 162 exonerations of people who death row. 20 of those have been by DNA evidence. So she certainly has a shot. But I think more likely the fingerprint running through the database -- that would be more impactful, that would probably get her out quicker. Reporter: For "Nightline," I'm linsey Davis in New York. Last defense" airs Tuesday night at 10/9 central right here on ABC.

This transcript has been automatically generated and may not be 100% accurate.

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