CHICAGO (AP) — A judge has ruled three men who say a fellow detainee confessed to fatally shooting a Chicago police officer in 2010 can testify at the man’s trial.

The Chicago Tribune reports Cook County Circuit Judge Stanley Sacks ruled in January the three inmates who said Anton Carter confessed to the shooting death of Officer Michael Bailey were credible witnesses.

Prosecutors say Carter shot the off-duty officer during an attempted carjacking. Carter was charged after allegedly bragging about the slaying while he was behind bars on an unrelated case.

The three men testified before Sacks last month under a law that took effect Jan. 1. It allows judges to assess the reliability of potential jailhouse informants before deciding whether they can take the stand. Such testimony has long been criticized as unreliable.

Carter’s trial is scheduled to begin May 13.