In 1984, after Herrera’s brother Raul was murdered, Raul’s attorney came forward and signed an affidavit stating that Raul told him he had killed Rucker and Carrisalez. A former cellmate of Raul also came forward and signed a similar affidavit. Raul’s son, Raul Jr., who was nine at the time of the killings, signed a third affidavit. It averred that he had witnessed the killings. Jose Ybarra, Jr., a schoolmate of the Herrera brothers, signed a fourth affidavit.
Ybarra alleged that Raul Sr. told him in 1983 that he had shot the two police officers. Herrera alleged that law enforcement officials were aware of Ybarra’s statement and had withheld it in violation of Brady v. Maryland. Armed with these affidavits, Herrera petitioned for a new trial, but was denied relief in state courts. One court did dismiss Herrera’s Brady claim due to lack of evidence. Herrera’s appeal eventually reached the U.S. Supreme Court, where it was argued in October 1992.
In January 1993, the U.S. Supreme Court ruled that Herrera's claim of actual innocence was not a bar to his execution. He had to show that there were procedural errors in his trial in order to gain relief. Justice Rehnquist wrote that the "presumption of innocence disappears" once a defendant has been convicted in a fair trial. Dissenting Justice Blackmun wrote: "The execution of a person who can show that he is innocent comes perilously close to simple murder." Herrera was executed by lethal injection on May 12, 1993, four months after the ruling.
Herrera declined a last meal. His final statement was: