The state’s highest court ruled on Wednesday that prosecutors had no obligation to confirm for a defendant that his victim in a shooting was a confidential informant, in a ruling that offers further protection to those who cooperate with police.

The Supreme Judicial Court, overturning a lower court judge’s decision in a Boston case, unanimously rejected the defense’s assertion that the status of the victim factored into the defendant’s “state of mind” when he committed what he said was an act of self-defense.