Robert Lynn Pruett (September 18, 1979 – October 12, 2017) was a Texas man convicted and executed for the 1999 murder of TDCJ Correctional Officer Daniel Nagle. Pruett had been certified as an adult at 16 and was already serving a 99-year sentence for his involvement in the murder of Ray Yarborough, which occurred when Pruett was 15. Pruett was convicted along with Howard Steven "Sam" Pruett Sr., his father, who received a life sentence for his participation in the murder, and Howard Steven Pruett Jr., his brother, who received a 40-year sentence. Howard Sr. testified that neither son took part in the killing, as did Robert, who was nonetheless convicted under the Texas law of parties. Details of both the Yarborough and Nagle murders were featured in the BBC documentary Life and Death Row - Crisis Stage.

Pruett also denied involvement in Nagle's murder and his defense attorney stated that "what convicted him was the testimony of four or five convicts who received deals, of one kind or another, in exchange for the testimony against Pruett". For example, one witness, Harold Mitchell, testified that he had been offered a move to another prison in Virginia, near his family if he would testify that Pruett killed Nagle. If he did not, Mitchell would be charged with the murder of Nagle. The state relied on the testimony of Lisa Baylor, a forensic analyst who testified, using a now-debunked scientific method called "physical matching". Baylor linked the tape round the handle of the shank used to murder Nagle with a prison craft shop where a cellmate of Pruett worked.

Pruett died by lethal injection on October 12, 2017, after appeals for clemency to the Texas Board of Pardons and Paroles were rejected. Pruett started chanting during the execution and was visibly scared. Pruett was represented by the Texas Innocence Network and his attorneys pursued his innocence claim by appealing the denial of his DNA relief through the courts.

While in the Texas death row at the Polunsky Unit near Livingston, Pruett received 4 stays of execution.

Despite publicly maintaining his innocence, Pruett reportedly confessed in private to a pen pal in 2003. According to the story, Pruett said he had not intended to kill Nagle and regretted it.

A Nueces County jury found Pruett guilty of capital murder on April 24, 2002. The only witnesses to Nagle's murder were inmates. Nagle, who was the president of the AFSCME union local that represents McConnell guards, had complained that low pay, high turnover, and poor training of staff were turning Texas prisons into powderkegs. Nagle told supporters at the rally at the Governor's Mansion that "someone would have to be killed" before TDCJ got the message. He was murdered two weeks later.

There was no physical evidence linking Pruett with the murder, which he claimed he did not witness or participate in. When the murder weapon was tested for DNA, nothing conclusive was found. Nagle was killed as a result of a stabbing with a prison shank.

Pruett claimed he was framed by corrupt inmates and prison guards. Some Correctional Officers stated that corrupt Correctional Officers, known colloquially as "dirty bosses", were in league with prison gangs, and that they and their gang associates inside were involved with his murder. Weeks after the stabbing, Correctional Officers at the McConnell Unit were indicted for colluding with inmates to traffic drugs. Eliseo Martinez, one of the Correctional Officers interviewed during the investigation into Nagle's death, was arrested in late January 2000 for transporting a package believed to have contained $60,000 in laundered drug profits for inmates. Martinez claimed Pruett had told him he possessed a homemade shank during the investigation.