RAPID CITY, S.D. - A South Dakota jury convicted a Canadian man of murder Friday in the decades-old killing of an American Indian Movement activist whose death came to symbolize AIM and its often violent struggles with federal agents during the 1970s.

John Graham, a 55-year-old from the Southern Tutchone First Nation in the Yukon who was a member of the group, was convicted of felony murder during the kidnapping of Annie Mae Aquash of Nova Scotia. The jury acquitted him of premeditated murder.

Attorney General Marty Jackley, who prosecuted the case, said both murder charges carry a mandatory sentence of life in prison. Jackley said he wasn't sure whether parole was an option.

The 35-year investigation "has finally come to find justice," Jackley said afterward.

Prosecutors alleged Graham and two other AIM activists killed Aquash because they thought she was a government informant. Graham's attorney, John Murphy, didn't call any witnesses but questioned the reliability of several prosecution witnesses.

Jurors took a day and a half to return its verdicts for Graham after briefly telling the judge late Friday that they had deadlocked on one of the charges. They soon returned with decision on both counts.

"We waited 35 years," said Denise Maloney Pictou, one of Aquash's daughters. "It's been a long road for us."

Graham gazed straight ahead and didn't move as the verdicts were read. His daughter, Naneek, began to weep as the jury, one by one, stood to affirm the verdicts. Graham's family members did not comment as they left the courtroom.

During five days of testimony, prosecution witnesses testified that they saw Graham and two other AIM supporters, Arlo Looking Cloud and Theda Clark, tie Aquash's hands and place her in the back of a red Ford Pinto. The three took Aquash from Denver toward the Pine Ridge reservation, witnesses testified.

A key prosecution witness was Looking Cloud, who was convicted six years ago for his role in Aquash's murder and is serving life in prison. Looking Cloud said he stood nearby as Graham shot Aquash.

And two federal agents, former U.S. Marshal Robert Ecoffey and Bureau of Indian Affairs agent Mitch Pourier, said they saw Graham become nervous and talk about going to jail after they asked him about the murder in 1994.

But a number of expected prosecution witnesses -- including Serle Chapman, a British writer who interviewed Graham, and Thelma Rios, who pleaded guilty in November in connection with Aquash's kidnapping -- didn't take the stand.

The defence called no witnesses. Instead, Murphy questioned several prosecution witnesses -- particularly Looking Cloud -- on conflicts between their testimony and statements they had made before. Murphy accused Looking Cloud of embellishing his story and treating Graham like a "meal ticket" to a more lenient prison sentence.

Murphy wasn't available for comment after the verdicts were read. Graham's daughter and relatives did not comment as they left the courthouse.

The conviction comes after an investigation that started shortly after Aquash's body was found in February 1976. For years, witnesses refused to come forward. But authorities began to make progress in the 1990s, and Graham and Looking Cloud were indicted in federal court in 2003.

Graham was extradited four years later, but the federal charges against him were thrown out because neither he nor Aquash were American citizens. A state court then indicted Graham last year.

Aquash, a member of the Mi'kmaq tribe of Nova Scotia, was 30 when she died. Her death came about two years after she participated in AIM's 71-day occupation of the South Dakota reservation town of Wounded Knee.

AIM was founded in the late 1960s to protest the U.S. government's treatment of American Indians and demand the government honour its treaties with Indian tribes. It gained national attention in 1972 when it took over the Bureau of Indian Affairs headquarters in Washington but has since faded from public view.