A U.S. District Court judge has upheld a magistrate judge's decision that two men charged with the 1975 slaying of a fellow American Indian Movement (AIM) member can be tried together.

John Graham and Richard Marshall will stand trial May 12 in Rapid City, South Dakota, on charges related to the murder of Annie Mae Pictou-Aquash, a Mi'kmaq from Pictou, N.S.

In January, a U.S. magistrate judge also denied their requests for separate trials.

Graham, a former Yukoner, and Marshall, of Rapid City, S.D., have pleaded not guilty to charges they committed, or aided and abetted the first-degree murder of Pictou-Aquash.

Pictou-Aquash, 30, was shot in the head on Pine Ridge Indian Reservation. Her body was found 33 years ago in the Badlands near Wanblee, S.D.

Marshall was indicted in August, five years after Graham and another man, Fritz Arlo Looking Cloud, were initially charged.

Looking Cloud aiding prosecutors

Looking Cloud was convicted in 2004 for his role in Pictou-Aquash's murder and sentenced to life in prison. He is co-operating with prosecutors in their case against Graham and Marshall.

Witnesses at Looking Cloud's trial said he, Graham and Theda Clarke drove Pictou-Aquash from Denver in late 1975 and that Graham shot her as she begged for her life.

Clarke, who lives in a nursing home in western Nebraska, has not been charged.

Graham has denied killing Pictou-Aquash, but acknowledged being in the car from Denver.

The American Indian Movement occupied Wounded Knee on the Pine Ridge reservation during a standoff in 1973 that included a gunfire exchange with federal agents.

Pictou-Aquash's death has been surrounded in controversy, with speculation she was assassinated either by agents with the United States Federal Bureau of Investigation or by senior members of the American Indian Movement who believed she was a police informant.