The decision, by an 8-to-1 vote, was the latest in a series of Supreme Court decisions suggesting a pattern of prosecutorial misconduct in the Orleans Parish District Attorney’s Office. Justice Clarence Thomas dissented.
Tuesday’s case concerned Juan Smith, who was convicted of killing five people in 1995, when a group of men burst into a house in search of money and drugs. They ordered the occupants to lie down and opened fire.
Mr. Smith was the only person tried for the killings. He was convicted based solely on the eyewitness testimony of a survivor, Larry Boatner. Prosecutors presented no DNA, fingerprints, weapons or other physical evidence.
But Mr. Boatner’s testimony proved sufficient.
“He’s right there,” Mr. Boatner said at Mr. Smith’s trial, pointing at the defendant. “I’ll never forget him.”
It later emerged that prosecutors had failed to disclose reports of interviews with Mr. Boatner. In one, hours after the killings, Mr. Boatner said he could not describe the intruders except to say they were black men. Five days later, he said he had not seen the intruders’ faces and could not identify them.
Eyewitness evidence, according to recent studies and court decisions, is both unusually persuasive and unusually unreliable. Kannon K. Shanmugam, a lawyer with William & Connolly who represented Mr. Smith in the Supreme Court, told the justices in a brief that the withheld statements from Mr. Boatner “constitute the epitome of impeachment evidence.”
There was no question, Chief Justice John G. Roberts Jr. wrote for the majority, that the reports should have been turned over under Brady v. Maryland, a 1963 Supreme Court decision that requires prosecutors to provide favorable evidence to the defense. The question for the justices was only whether the failure mattered — that is, in the words of a 2009 decision, whether “there is a reasonable probability that, had the evidence been disclosed, the result of the proceeding would have been different.”
In a brisk four-page opinion in the case, Smith v. Cain, No. 10-8145, Chief Justice Roberts wrote that “Boatner’s undisclosed statements were plainly material.”
Prosecutors and Justice Thomas gave various reasons why the jury might have discounted the statements, including that Mr. Boatner was under stress and feared retaliation. Chief Justice Roberts dismissed the arguments as speculation and said the fact that the jury might have disbelieved the statements “gives us no confidence that it would have done so.”
The current district attorney, Leon Cannizzaro, said his office “will file a motion in this quintuple murder case to set it for trial within the next 60 days.”
Justice Thomas’s dissent, at 19 pages, was almost five times as long as the majority opinion. “The question presented here is not whether a prudent prosecutor should have disclosed the information that Smith identifies,” Justice Thomas wrote.
Rather, he wrote, the question was whether Mr. Smith had not shown a reasonable probability that the jury would have reached a different conclusion had it known of the undisclosed statements. Justice Thomas said a careful review of the balance of the evidence demonstrated that nothing would have changed.
The district attorney’s office has a history of inattention to the requirements of the Brady decision. The Orleans Public Defender’s Office, in a brief supporting Mr. Smith, said that 28 convictions obtained by the district attorney’s office were later ruled to have been tainted by Brady violations. The district attorney’s office said in its own brief that the correct number was 13.
Last March, in a 5-to-4 decision, the Supreme Court wiped out a $14 million award to John Thompson, a former death row inmate who was exonerated after 18 years when withheld evidence came to light.
Justice Thomas wrote the majority opinion in that decision, which divided along ideological lines. While he said prosecutors there had violated their duty to see justice done, he wrote that Mr. Thompson could not sue the office on the theory that it had failed to train its prosecutors.