A judge has agreed to hold a hearing next month on a request for a new trial from a man convicted in the 1993 killing of a Boston police detective.

Sean Ellis has been imprisoned for 20 years in the shooting death of Detective John Mulligan.

Ellis and another man were convicted of killing Mulligan as he slept in his car outside an all-night pharmacy.

Ellis' attorney says police never told his trial lawyers that one officer had accused another officer of killing Mulligan. The attorney alleges Mulligan was part of a group of corrupt officers who robbed criminals, which prosecutors deny.

Prosecutors say the jury that convicted Ellis had ample evidence, including statements from witnesses who said they saw Ellis near Mulligan's car and speeding away in another car.