RAPID CITY, S.D. (AP) – Defense attorneys in a 1975 slaying on a South Dakota Indian reservation say the government’s key witness should not be allowed to testify in next month’s trial.

John Graham and Richard Marshall are charged in federal court with murder and aiding and abetting in the death of American Indian Movement activist Annie Mae Aquash. Trial is scheduled to begin Feb. 16 in Rapid City.

Marshall’s attorney, Dana Hanna, says in court documents that he believes Arlo Looking Cloud intends to give testimony that the government knows is false. Looking Cloud was convicted of murder in 2004 for his role in Aquash’s death and was sentenced to life in prison.

Hanna says his motion is based on tape recordings of Looking Cloud’s telephone conversations from jail. Federal prosecutors say they are working on a response and declined further comment.