Duane Buck was sentenced to death after he was convicted more than 20 years ago for shooting two people to death - including his ex-girlfriend.
This undated photo provided by the Texas Department of Criminal Justice shows inmate Duane Buck.
The decision "made clear that there is no place for racial bias in the American criminal justice system", said Christina Swarns, litigation director of the NAACP Legal Defense and Educational Fund, adding that "the court has reaffirmed the long-standing principle that criminal punishments - particularly the death penalty - can not be based on immutable characteristics such as race". What was contested at the Supreme Court was what happened at the hearing into whether he deserved the death penalty. In Texas death penalty trials, one of the "special issues" jurors must consider when deciding punishment is whether the defendant they've convicted would be a future danger.
At trial, Buck's lawyer called a witness to the stand who testified that Buck was more likely to be unsafe in the future because he's black.
Quijano testified that he thought Buck was unlikely to commit future violent attacks but acknowledged that he could "never rule out" the possibility.
"Dr. Quijano responded that certain factors were "know [n] to predict future dangerousness" and, consistent with his report, identified race as one of them".
Roberts continued: "If the jury did not impose a death sentence, Buck would be sentenced to life in prison and no such romantic relationship would be likely to arise".
The Supreme Court has rejected an appeal from a Virginia death row inmate who killed two people during an escape in 2006.
But as the high court noted Wednesday, despite Buck's case being among those Cornyn's office identified as similar to Saldano's, it was not among those in which prosecutors admitted error and allowed new sentencing hearings. Chief Justice John Roberts said in his majority opinion that the federal appeals court that heard Buck's case was wrong to deny him a hearing.
"No competent defence attorney would introduce evidence that his client is liable to be a future danger because of his race", Mr Roberts wrote. "The court has reaffirmed the longstanding principle that criminal punishments - particularly the death penalty - can not be based on immutable characteristics such as race". His case was among six in 2000 that then-Texas Attorney General John Cornyn in a news release said needed to be reopened because Quijano's statements were racially charged.
The case is Buck v. Davis.