The background of the Holmes case is as follows. On New Year's Eve in 1989 an 86-year-old woman was beaten, robbed and assaulted in her home. She later died of her injuries. Bobby Lee Holmes was arrested and charged with the woman's murder. Blood and fingerprint evidence linked Holmes to the crime. His lawyers said Holmes was innocent and pointed to witnesses who had seen another man, Jimmy White, near the woman's house on the night of the murder. Four witnesses said at a preliminary hearing that they had heard White admit to the crime or say Holmes was innocent. The trial judge excluded this evidence from Holmes' trial because prosecutors had "strong forensic evidence" of his guilt. He was convicted and sentenced to death.
The Supreme Court held that the rule applied in this case deprived Holmes of his constitutional rights. The efficacy and logic of the rule, according to the Court, depends on an accurate evaluation of the prosecution's proof, and the true strength of the prosecution's proof cannot be assessed without considering challenges to the reliability of the prosecution's evidence. Just because the prosecution's evidence, if credited, would provide strong support for a guilty verdict, it does not follow that evidence of third-party guilt has only a weak logical connection to the central issues in the case. Such credibility and reliability determinations are for the triers of fact and not the courts.
Writing for the unanimous Court, Justice Alito made this point about the South Carolina rule:
The rule applied in this case is no more logical than its
converse would be, i.e., a rule barring the prosecution from
introducing evidence of a defendant's guilt if the defendant
is able to proffer, at a pretrial hearing, evidence that, if
believed, strongly supports a verdict of not guilty. In the
present case, for example, the petitioner proffered
evidence that, if believed, squarely proved that White, not
petitioner, was the perpetrator. It would make no sense,
however, to hold that this proffer precluded the prosecu-
tion from introducing its evidence, including the forensic
evidence that, if credited, provided strong proof of the petitioner's guilt.