Early on the morning of January 31, 2002, Robert Roberson walked into an emergency room in East Texas. His two-year-old daughter Nikki was in his arms. She was limp and unresponsive. Her lips were blue. Hospital staff placed Nikki on life support and attempted to revive her.

And they called the police on Roberson. They thought they had shaken baby syndrome.

But as he testified before the Texas Legislative Judiciary Committee on Wednesday, Dr. Roland AuerA Canadian neurosurgeon who has testified in similar cases said Nikki was not a victim of abuse.

“Nikki died as a result of pneumonia – cardiac arrest – and was essentially brain dead in a living body,” Auer said.

At the time, medical experts were advised to monitor for deaths from shaken baby syndrome. Auer said the medical diagnosis was incorrect.

“But what should you do if you see bleeding on the inside and nothing on the outside? “You have to come up with a theory, and that's how the shaken (baby) theory came about,” he told lawmakers. And then it becomes a question of 'Who did this?' instead of 'What happened?'”

The American Academy of Pediatrics says shaken baby syndrome — now called “abusive head trauma” — remains a significant cause of death and injury in children. The academy recommends pediatricians be alert for signs of an abusive head injury.

Roberson is on the autism spectrum. The arresting officer said the fact that he did not respond emotionally about the medical crisis or Nikki's death contributed to his being arrested for her murder.

The arresting officer, Brian Wharton, told Texas lawmakers Wednesday that he is haunted by what happened to Roberson.

“I'm ashamed that I was so focused on finding a perpetrator and convicting someone that I didn't see Robert,” Wharton said.

Since Roberson's conviction and death sentence, new research shows that shaken baby syndrome is more complex than was thought just 20 years ago.

Yet Roberson has been on death row in Texas for over 22 years. Appeals for the courts to reconsider the new evidence were rejected.

Wharton said the appeals system was introduced with the understanding that bad convictions sometimes occur.

“It’s all pointless if no one admits we did anything wrong,” Wharton said.

Roberson was convicted in Anderson County in 2003.

District Attorney Allyson Mitchell testified Wednesday that Roberson had a fair trial – including an adequate defense.

On Wednesday, the Texas Board of Pardons and Paroles rejected clemency requests.

Texas Governor Greg Abbott can only grant a one-time extension of 30 days. Texas House Representative Jeff Leach (R-Plano) asked Roberson to appear before the committee at a later date to force a delay. It's unclear how the state or Abbott will respond, given Thursday's execution date.

Roberson's lawyers are now appealing to the U.S. Supreme Court, claiming he was denied due process and that Texas courts refused to hear evidence of his actual innocence.

Speaking to TPR from death row in Texas, Roberson said he accepts his fate. He relies on his deep faith in God's will.

“But I’m at peace when I go over there, you know,” he said. “I don’t want to go there.” Don’t get me wrong.”

Unless there is intervention, Roberson will die by lethal injection Thursday evening.