RAPID CITY, South Dakota (AP) – After years of delays and legal wrangling, a murder trial began Wednesday for a Native Canadian man accused of shooting an American Indian Movement activist 35 years ago on a reservation.

South Dakota Attorney General Marty Jackley recounted for jurors what investigators believe happened in the three days leading up to the December 1975 slaying of Annie Mae Aquash on South Dakota's Pine Ridge reservation. He said the defendant, John Graham, 55, shot her because the activist group's leaders thought she was a government informant.

Graham's attorney, John Murphy, countered in his opening statement that the prosecution lacked a murder weapon, fingerprints or other physical evidence to link Graham with Aquash's killing or the site of her death.

Graham, a Southern Tutchone tribal member from Canada, is charged with first- and second-degree murder. He could be sent to prison for life if convicted.

Aquash's death became synonymous with the American Indian Movement and its often violent struggles with federal agents in the 1970s. Family members and observers have said Graham's trial could help answer lingering questions about why Aquash died and who ordered her killing.

During his narrative about what the state believes happened, Jackley told jurors that Graham and two other AIM activists, Arlo Looking Cloud and Theda Clark, were told in late 1975 to take Aquash from Denver to Rapid City, to the apartment of Thelma Rios.

Graham, Looking Cloud and Clark then took Aquash to the Rosebud and Pine Ridge reservations, and eventually stopped near a highway on Pine Ridge, Jackley said.

"John Graham knew the task at hand and he got out of the vehicle,'' Jackley said. The prosecutor said Graham then shot Aquash in the back of the head as Looking Cloud stood nearby.

Looking Cloud was found guilty of his involvement in the murder in 2004 and will likely testify at Graham's trial. Rios pleaded guilty last month in connection with Aquash's kidnapping and may also testify.

The prosecution called five witnesses Wednesday, including federal agents who first investigated Aquash's death after her unidentified body was found in February 1976.

Aquash, a member of the Mi'kmaq tribe of Nova Scotia, was 30 when she died. Her death came about six months after two FBI agents were gunned down in a shootout with AIM members, and two years after she participated in AIM's 71-day occupation of the South Dakota reservation town of Wounded Knee.

Former FBI special agent John Munis testified about how a pathologist removed Aquash's hands from her corpse in a lab in Washington to analyze them for fingerprints. Her cause of death was mistakenly listed as exposure to the cold, and her body was buried in March 1976 – before it was identified.

Former FBI special agent William Wood testified that he requested Aquash's body be exhumed after learning her identity. A second pathologist found a .32-caliber bullet.

Former Bureau of Indian Affairs officer Nathan Merrick said he noticed what looked like dry blood near Aquash's head when he arrived where her body was discovered. During cross-examination, Murphy said the FBI didn't note foul play on its initial reports. Merrick replied: "That's a question for them.''

Roger Amiotte, the rancher who found Aquash's body, and Ray Hand Boy, who drove Aquash to Denver in November 1975, also testified. More witnesses are expected Thursday.

Jackley said witnesses would show that AIM leaders considered Aquash dangerous and that Graham later suggested he felt remorse for the crime.

Murphy questioned the credibility of two witnesses he said were central to the prosecution's case: Looking Cloud and Serle Chapman, a British journalist who interviewed Graham and cooperated with the FBI.

Murphy accused Looking Cloud of changing his story in the hope of having his life sentence reduced, and Chapman of lying to get money and help with immigration from the FBI.

AIM was founded in the late 1960s to protest the U.S. government's treatment of Native Americans and demand the government honor its treaties with tribes.

It first gained national attention in 1972, when it took over the Bureau of Indian Affairs headquarters in Washington, but has since faded from public view.

Graham was first indicted in 2003, and extradited to South Dakota four years later to face federal murder charges. But after federal courts ruled that U.S. prosecutors didn't have authority to prosecute Graham, he was indicted in state court.