supreme court
People stand outside the Supreme Court building at Capitol Hill in Washington D.C., Feb. 13, 2016. Reuters/Carlos Barria

A death row inmate's appeal can continue because an expert witness at his original trial said blacks were more likely to be dangerous than other races, the Supreme Court ruled Wednesday.

In a 6-2 decision, the Court ruled that Duane Buck, now 53, was entitled to continue to appeal the death sentence he received for the 1995 murder of his ex-girlfriend, Debra Gardner, and her friend, Kenneth Butler. Buck also shot his stepsister, who survived.

Buck was found guilty of the murders, and the jury in the case was charged with determining if Buck should be sentenced to death. As the Court noted, in order to hand down a death sentence, the jury had to determine that Buck would likely "commit criminal acts of violence that would constitute a continuing threat to society." During the sentencing phase of his trial, Buck's own attorney called upon Dr. Walter Quijano, who testified on behalf of prosecutors in more than 100 capital murder cases, to delivery expert testimony.

During cross-examination, the prosecutor in the case asked Quijano if "the race factor, black, increases the future dangerousness" of Buck. Quijano replied that Buck's race did indeed make him more likely to be dangerous in the future. In spite of another psychologist testifying that Buck was not likely to be dangerous in prison, as he had served time without incident in the past and that the murders were a "crime of passion," the jury sentenced Buck to death after asking for Quijano's report during deliberation.

On Wednesday, the court rejected the state's argument that Quijano hardly mentioned race in his testimony, and therefore wasn't the main factor in the jury's decision to put Buck to death.

"When a jury hears expert testimony that expressly makes a defendant’s race directly pertinent on the question of life or death, the impact of that evidence cannot be measured simply by how much air time it received at trial or how many pages it occupies in the record," Chief Justice John Roberts wrote in his majority opinion. "Some toxins can be deadly in small doses."

The decision, which also found that Buck's attorney failed to provide a competent defense by putting Quijano on the stand, sent Buck's appeal back to the 5th U.S. Circuit Court of Appeals in New Orleans, which previously refused to hear Buck's case. In 2000, then-Texas attorney general John Cornyn said six cases would be reopened due to Quijano's faulty and racially-charged testimony. In five of those cases, new punishment hearings were held. In all five, the defendant was once again sentenced to death, CBS News reported in October. Buck's was the sixth case mentioned by Cornyn, who is now a U.S. senator.

Justice Clarence Thomas dissented with the majority and was joined by Justice Samuel Alito.

"Having settled on a desired outcome, the Court bulldozes procedural obstacles and misapplies settled law to justify it," Thomas wrote in his dissent.