In a highly unusual ruling, a judge yesterday excused a terrified witness in a murder trial from testifying against the defendant, a reputed gangbanger, saying prosecutors could instead present to the jury records of what he had told the cops.

The witness, Theodore Edwards, 22 — who had been beaten by a group of attackers in 2009 and shot in the arm just last week — made a brief appearance in Bronx Supreme Court, wearing a bandage.

He said he wouldn’t testify against Brandin Santiago, who’s accused of firing into a crowd outside a party in 2008, killing prep school student Nadairee Walters.

“He is a truly frightened witness,” said Justice Ann Donnelly,

DA investigator Peter Moro, who tried unsuccessfully to get Edwards to take the stand, said, “He felt bad about the victim, a 17-year-old girl. He wished he could do something but he was too afraid.”