One of the goals of criminal prosecutors is to make the jury believe that they have an airtight case. They would like the jury to think that all of the evidence and witness testimony points clearly to the guilt of the suspect. But as much as they may not want to, prosecutors are required to disclose evidence that is likely to demonstrate that the suspect is innocent; this is commonly referred to as exculpatory evidence.

In a decision yesterday, the U.S. Supreme Court overturned a conviction of criminal suspect because the prosecution in the case had not disclosed exculpatory material evidence. This was evidence that would have weakened the prosecution’s case if it had been made available to the criminal suspect.

In yesterday’s decision, Smith v. Cain, the case against the criminal suspect was based almost completely on the testimony of a single witness. There were no other witnesses or physical evidence that linked the suspect to the crime. But this single witness had told the jury that he had “no doubt” that this suspect had committed the crime, and that he had stood “face to face” with the suspect during the encounter.

On their own, those statements from the witness could sound compelling. But the prosecution knew that the witness had not always been quite as certain of the identity of the suspect. During the investigation, the police interviewed this witness. At that time, the witness said that he could not identify any of the perpetrators because he had not seen their faces. He also told the police investigators that he would not be able to identify the persons involved if he saw them.

These statements, in which the witness indicated that he could not identify anyone involved in the crime, were taken down in notes by the investigators. These notes were not disclosed to the criminal suspect in this case until he was able to obtain them as part of an appeal after his conviction.

The Supreme Court ruled that because this evidence was improperly withheld, and could have changed the outcome of the case, the conviction must be overturned.

Source: ABA Journal, “Supreme Court Tosses Murder Conviction for Brady Violation by New Orleans DA,” Debra Cassens Weiss, Jan. 10, 2012