Investigating the death of Brittney Brashers

Brittney Brashers' wrecked car — Denver Police Dept.

At approximately 1:40 a.m. on Nov. 17, 2009, 22-year-old Brittany Brashers' car crashed on a dead-end street in Denver, Colo.

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Denver resident Steve Sanchez was visiting a friend when he heard a loud bang outside on the street. He jumped up, went outside, saw the accident scene and immediately called 911.

Video: Steve Sanchez' 911 call
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Sanchez described the scene to the 911 operator: A woman was in the driver's seat of the crashed car and a was man holding her in his arms, he was shaking her as he kept saying "Brittney, Brittney."

Video: Steve Sanchez' 911 call
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The man cradling Brittney in his arms was her on-again, off-again boyfriend, Robert "Robbie" Walters.

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Brittney and Robbie met while stationed in Iraq as members of the United States Air Force. The night of the wreck, Robbie was wearing his seat belt and survived the crash. Brittney had not worn her seat belt.

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John and Brittney Brashers — Brashers family

At first, it looked like the young, bright, attractive and athletic Brittney, seen here with her brother, John, had been the victim of a tragic car accident.

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Barry and Brittney Brashers — Brashers family

Things didn't add up for Brittney's father, Barry Brashers. When he heard Brittney had not been wearing a seat belt on the night of the crash, a red flag went up for him. "She would never move a car without ... puttin' her seat belt on. Never."

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Dert. Troy Bisgard, Denver Police Dept. — CBS News

Investigators, including homicide detective Troy Bisgard, were troubled by the crash scene. It looked staged. Why was the car found at the end of a dead-end residential street? Were Brittney and Robbie lost?

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Medical examiner Dr. John Carver — CBS News

Medical Examiner John Carver also had questions about how Brittney died. His autopsy revealed that she didn't have any significant injuries to her limbs, internal organs, neck, spinal cord, skull or brain.

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The injuries Brittney did have were not what Dr. Carver expected to see. His examination revealed pinpoint hemorrhages on the skin of her face and surrounding her eyes. These were tell-tale signs that she might have been strangled.

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Strangulation was hard for Dr. Carver to confirm because Brittney was born without a piece of cartilage in her throat -- cartilage that is often crushed in strangulation. With no physical evidence to prove that she was strangled, the medical examiner had no choice but to list Brittney's cause of death as "undetermined."

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"Undetermined" meant no ruling of homicide. Still, Det. Bisgard felt that Brittney's death was not an accident. The more he learned about Robbie Walters, the more convinced he was that Brittney was murdered.

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Brittney Brashers was an athletic young woman who played on an all-girls football league. On the night of the accident, she went to a nightclub for a photo shoot with the rest of her teammates. Robbie ended up coming to the photo shoot even though he and Brittney had broken up yet again.

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Friend and teammate Brittany Austin-Goyne told "48 Hours" that at one point during the photo shoot, all of the girls took their tops off. They posed strategically, with props in order to appear sexy without really showing anything. Austin-Goyne told "48 Hours" that after Brittney took off her top, Robbie Walters started to cry and took photos of Brashers with his cell phone.

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Detective Bisgard discovered early in his investigation that Robbie Walters was married and that he had been arrested after a physical fight with Brittney. While examining Brittney's phone, police found a profanity laced message from Robbie. In that message, Walters said that he hoped that Brittney would die.

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Det. Troy Bisgard, Denver Police Dept. — CBS News

Detective Bisgard wanted to talk to Robbie Walters' wife, Elena, but he knew that he couldn't force her to talk to him. Then, four months into the investigation, Bisgard got word that Robbie had had a big fight with his wife. Looking for any possible shred of new evidence, he gave Elena a call. He said that once she started talking, she never stopped.

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48 Web Extra 911 Girl Punch Conversation - Collision Course

Elena Walters told Det. Bisgard that Robbie had confessed repeatedly to her that he had killed Brittney. She also told Bisgard that she secretly made over a dozen cell phone recordings of her conversations with Robbie. In these recording he gives graphic and precise details of how he beat and strangled Brittney.

Video: Robbie Walters' cell phone confession
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Dr. John Carver, the medical examiner, told "48 Hours" that Robbie's confessions explained the things that had puzzled him at the conclusion of Brittney's autopsy. Her injuries fit very well with Robbie's description of how he punched and choked her.

Video: Robbie Walters' cell phone confession
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Robbie Walters mug shot — Colorado Dept. of Corrections

Elena Walters' information was all Dr. Carver needed to change the manner of Brittany Brashers' death from "undetermined" to homicide. Three days after talking with Elena, Det. Bisgard arrested Robbie Walters.

Video: Robbie Walters' cell phone confession
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Prosecutors Helen Morgan and Phil Geigle now had plenty of ammunition to build a case. At trial, they use Robbie's own recorded words against him. They theorized that on the night that she died, Brittney and Robbie got into an argument after the photo shoot, he lost his temper and he killed her. Robbie Walters was convicted and sentenced to life without parole.

Video: Robbie Walters' cell phone confession
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Brittney Brashers with her sister, Sara. — Brashers family

At Robbie's sentencing, Brittney's sister, Sara, seen here, addressed the court on behalf of her family. Despite being nervous, she wanted everyone in the courtroom to hear her memories of her beloved sister.

Video: Brittney's sister speaks out
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