The Texas Supreme Court on Thursday spared the life of death row inmate Robert Roberson, granting a rare stay of execution as prison officials were poised to administer his lethal injection.

The Supreme Court's decision came after days of legal wrangling and a furious effort by a bipartisan group of Texas lawmakers to stop Roberson's execution for the death of his 2-year-old daughter Nikki in 2002. Strong evidence suggests that Roberson is innocent and was convicted based on Shaken Baby Syndrome, which has been largely debunked.

Roberson had been set to die at 6 p.m. CT but the lawmakers' efforts successfully delayed the execution for hours, and ultimately, stopped it − a development rarely seen in the nation's most prolific death penalty state.

"After being told about the stay, he (Roberson) praised God and thanked his supporters," said Amanda Hernandez, a spokeswoman for the Texas Department of Criminal Justice, which carries out executions.

The last-minute reprieve followed a series of crushing defeats for Roberson's defense attorneys and the lawmakers. The Texas Board of Pardons and Paroles declined to recommend clemency for Roberson on Wednesday. And on Thursday, the U.S. Supreme Court declined to stop the execution, saying that Roberson's attorneys hadn't raised a federal issue the high court had the power to address. And the Texas Criminal Court of Appeals has repeatedly denied efforts to stop the execution, most recently on Thursday.

The decision by the Texas Supreme Court to grant a stay of execution was the result of a move by five Republican and four Democratic lawmakers on the Texas House Committee on Criminal Jurisprudence, who issued a subpoena for Roberson late Wednesday in an extraordinary effort to intervene in his execution.

Texas Reps. Joe Moody, a Democrat, and Jeff Leach, a Republican, have been leading the charge for Roberson's reprieve and issued a joint statement late Thursday thanking the Texas Supreme Court "for respecting the role the Texas legislature in such consequential matters."

"For over 20 years, Robert Roberson has spent 23.5 hours of every single day in solitary confinement in a cell no bigger than the closets of most Texas, longing and striving to be heard," they said. "And while some courthouses may have failed him, the Texas House has not ... We look forward to welcoming Robert to the Texas Capitol, and along with 31 million Texans, finally giving him − and the truth − a chance to be heard."

Here's what you need to know.

What was Robert Roberson convicted of?

Roberson was convicted of killing his 2-year-old daughter Nikki in their home in the East Texas city of Palestine in 2002.

Roberson reported hearing Nikki cry and finding that she had fallen out of bed. After soothing her, he said they both went back to sleep. Later, when Roberson woke again, he found Nikki wasn’t breathing, and her lips had turned blue. At the emergency room, doctors observed symptoms consistent with brain death and she was pronounced dead the next day.

While doctors and investigators at the time jumped to the conclusion that Nikki died of Shaken Baby Syndrome, the toddler had pneumonia in both lungs, pre-existing conditions for which she was prescribed opioids now banned for children, and undiagnosed sepsis.

Shaken Baby Syndrome has been largely debunked as junk science, and the lead investigator in Roberson's case told USA TODAY's The Excerpt podcast that he botched the investigation.

"Robert is a completely innocent man and we got it completely wrong, because we were looking for the wrong things," Brian Wharton said, adding that his confirmation bias and a number of misunderstandings wrongly pointed him to Roberson's guilt.

"I was wrong. I didn't see Robert. I did not hear Robert," Wharton said. "I can tell you now, he is a good man. He is a kind man. He is a gracious man. And he did not do what the state of Texas and I have accused him of."

Who has been fighting to stop Robert Roberson's execution?

Perhaps the most remarkable voices fighting for mercy for Roberson have been pro-death penalty Republican lawmakers working with Democrats on the issue.

Last month, a bipartisan group of 84 Texas lawmakers urged the state's Board of Pardons and Paroles to recommend clemency for Roberson "out of grave concern that Texas may put him to death for a crime that did not occur.”

“It should shock all Texans that we are barreling towards an execution in the face of this new evidence,” wrote the Texas Legislature members. “Other states look to Texas as a leader for both enforcing the rule of law and addressing wrongful convictions. We now look to you to prevent our state from tarnishing that reputation by allowing this execution to proceed.”

The clemency board denied their request.

In addition to the lawmakers fighting for Roberson, 34 scientific and medical experts wrote to the clemency board explaining that had Nikki died today, "no doctor would consider Shaken Baby Syndrome" as the cause because the condition "is now considered a diagnosis of exclusion."

"Nikki’s pneumonia, the extreme levels of dangerous medications found in her system during her autopsy, and her fall from the bed explain why Nikki died," the experts wrote.

Also calling for Roberson's salvation: groups representing parental rights, autism advocates, faith leaders and anti-death penalty groups including the Innocence Project, and bestselling author John Grisham.

"Nikki’s death was a tragedy, not a crime," Grisham wrote in a column for the Palestine Herald-Press. "Robert Roberson may be out of options unless Texas authorities recognize the injustice of Mr. Robertson’s conviction and death sentence, reverse course, and grant him a new trial."

More about the efforts that led to the stay of execution

The dramatic path that led to the Texas Supreme Court's stay of execution began with the Texas House Committee on Criminal Jurisprudence, which heard hours of expert testimony in Roberson's case on Wednesday and unanimously voted to subpoena Roberson and schedule his testimony on Monday − four days after his execution.

The Texas Department of Criminal Justice, which carries out executions, was proceeding as scheduled Thursday despite the subpoena, telling USA TODAY that they were "preparing and planning to proceed as normal."

Shortly after that, Travis County Judge Jessica Mangrum heard arguments from Texas Republican Rep. Jeff Leach and Democratic Rep. Joe Moody, who were requesting a temporary restraining order of the execution so they could carry out the subpoena and hear Roberson's testimony. Mangrum granted the temporary restraining order but the state Attorney General's Office immediately appealed, and the Texas Criminal Court of Appeals overturned Mangrum's decision.

Although that avenue ultimately failed, Leach and Moody took the fight to the Texas Supreme Court, filing an emergency motion for a stay of execution to allow for Roberson's testimony Monday.

"If TDCJ (the Texas Department of Criminal Justice) follows through with executing Mr. Roberson on October 17, it willforever deprive the Committee from hearing Mr. Roberson’s valuable and relevant testimony to which it is entitled," they argued. "His testimony is extremely valuable to the Committee and the Texas public as it will further the Committee and Legislature’s policies of ensuring fair and just administration and execution of laws within their jurisdiction."

The Texas Supreme Court agreed to stop the execution to allow the testimony.

What happens now?

Roberson will presumably testify before the House committee on Monday. The committee is looking at the lawfulness of Roberson's conviction as it relates to Texas' so-called "junk science" law. The 2013 law allows people to challenge their convictions based on new scientific evidence.

In Roberson's case, the knowledge about Shaken Baby Syndrome has dramatically changed since the time of his arrest.

Roberson's execution can still be rescheduled.

Contribution: Taylor Wilson, Maureen Groppe