The Supreme Court has halted the execution of an African-American prisoner over evidence that a key prosecution witness expressed racial bias. Duane Buck was set to be put to death Thursday night for a 1995 double murder. Although Buck’s guilt is not in dispute, defense attorneys have challenged his death sentence over the testimony of a state psychologist during the trial. The psychologist, Walter Quijano, told jurors that sparing his life could be dangerous because African-American criminals are more likely to pose a future danger to the public. The Supreme Court has agreed to take up one of two appeals filed by Buck’s attorneys over Quijano’s testimony.