RAPID CITY, S.D. (AP) – The lawyer for a man accused in a 1975 slaying on a South Dakota Indian reservation says his client did not provide the murder weapon and says the government's key witness in the case has changed his story.

Richard Marshall has pleaded not guilty to aiding and abetting the shooting of fellow American Indian Movement activist Annie Mae Aquash, a Canadian who came to the Pine Ridge Indian Reservation in the early 1970s. The trial began Wednesday in federal court.

Prosecutor Robert Mandel said in opening statements that Marshall supplied a .32-caliber revolver and ammunition when AIM members John Graham, Arlo Looking Cloud and Theda Clarke stopped at Marshall's house near Allen the day Aquash was killed. Aquash had been abducted in Denver, where she was hiding from an illegal weapons charge, and driven to South Dakota in the back of Clarke's Ford Pinto, witnesses said.

Graham is accused of shooting Aquash in the back of the head. He awaits trial in state court.

“Mr. Marshall provided Theda Clarke with the revolver that was used to murder Annie Mae,” Mandel said, looking at the 58-year-old Marshall.

Defense attorney Dana Hanna said the three AIM members did not leave the house with a gun from Marshall because the decision to kill Aquash wasn't made until a few hours later. Marshall said Clarke asked Marshall and his wife, Cleo Gates, to provide clothes for Aquash before they left.

“They didn't ask for a change of clothes so she could have clean clothes when they assassinated her hours later,” Hanna said.

Prosecutors believe AIM leaders ordered her killed because they thought she was a government informant. Federal investigators have denied Aquash was a snitch.

Hanna told the jury that Looking Cloud, who is expected to testify for the government, said in previous interviews with police that he didn't remember stopping at Marshall's house. Looking Cloud changed his story in 2008, Hanna said.

Looking Cloud was convicted in 2004 for his role in Aquash's death and was sentenced to life in prison.

“Fritz Arlo Looking Cloud invented a lie to get out of federal prison,” Hanna said.

Aquash's frozen body was found on the South Dakota Badlands in February 1976. After many unsuccessful attempts to get the case to court, Graham and Looking Cloud were indicted in 2003.

“This is an incredibly old case, I understand that,” Mandel told jurors, “but there's nothing about the age of this case that makes it any less serious.”