Rapid City, S.D. - A federal jury on Friday convicted Arlo Looking Cloud in the 1975 execution-style slaying of Anna Mae Pictou Aquash, thought by some at the time to be a government informant against the American Indian Movement.

The jury of seven women and five men deliberated about seven hours.

Looking Cloud, 50, looked straight ahead and showed no emotion when the verdict was read. Some of his family members hung their heads. An aunt who raised him cried quietly.

He will be sentenced April 23 to a mandatory life prison term.

Aquash's frozen body was found in February 1976 on the Pine Ridge Indian Reservation. The 30-year-old Canadian woman had been shot in the head.

Federal agents investigated for years but didn't bring an indictment until March 2003, when Denver police arrested Looking Cloud.

Another man charged in the case, John Graham, was arrested in December in Vancouver, British Columbia, and plans to fight extradition.

They were charged with first-degree murder committed in the perpetration of a kidnapping.

Looking Cloud's attorney, Tim Rensch, said he will appeal and believes there is a good chance of winning an appeal because of hearsay evidence introduced in the trial.

He said prosecutors also put in a lot of prejudicial evidence that "had nothing to do with the case and could provide a substantial river of reasons for appeal."

U.S. Attorney Jim McMahon thanked all the law enforcement officers who have worked on the case the past 28 years, and he complimented the people who came forward to testify about what happened.

"I just talked with Denise (Maloney), Annie Mae's daughter, and she told me this brings a little closure for them. And that makes it all worthwhile," McMahon said.

McMahon said he's confident the case will stand up on appeal. He would not comment when asked if more indictments are coming.

"We're looking forward to a visit by Mr. Graham to South Dakota and then we'll take it one step at a time."

McMahon said Bob Ecoffey "opened up a lot of lines of communication on the reservation."

Ecoffey, a former U.S. marshal who now oversees Bureau of Indian Affairs law enforcement, started working the case in the 1990s and was the prosecution's final witness.

Ecoffey, who is likely to testify in the future, said only: "I'd just like to say that this case and this trial is not about the American Indian Movement. It's about justice for Anna Mae and her family."

Indian activist Russell Means, a former member of AIM, said he was angered at the verdict.

"I thought that South Dakota had raised some level above Neanderthalism. It's business as usual in the courts of South Dakota," Means said.

"Our culture is disregarded and not included and one of the most pathetic men in the city of Denver is given the sole responsibility for the murder ordered by a leader of the American Indian Movement," he said.

In closing arguments, McMahon said the case boils down to the fact that Looking Cloud helped take Aquash to the place where Graham killed her - despite opportunities to get away.

"She gets to the edge of the cliff and asks to pray and she's shot in the back of the head. You don't have to go any further in this case than that there. Because to haul somebody that distance to the edge of the cliff is premeditated, cold-blooded murder. There weren't any surprises. She begged all the way up," he said.

"He wasn't the outsider. He was the insider, along with the others."

Rensch argued that his client didn't know Aquash was going to be killed and that prosecutors have not proven he knowingly took part in it - something the law requires for a conviction. Merely being present isn't enough, he said.

"They have to prove beyond any reasonable doubt that in his mind he wanted Miss Pictou Aquash to die," Rensch said. "Tagging along isn't enough.

"Arlo Looking Cloud killed no one. Arlo Looking Cloud didn't pull the trigger that killed Miss Pictou Aquash."

Rensch said that if his client had been an active participant, he wouldn't have been so cooperative with investigators.

"Why would he take the authorities out there and show exactly what happened unless he was at the wrong place at the wrong time," he said.

Rensch said the killing was horrible. But he argued that Looking Cloud was young and didn't stick up for himself when he was told to help drive Aquash to Rapid City and eventually to the place where she was killed.

Being a witness to the killing ruined Looking Cloud's life, Rensch said.

His voice cracked as he criticized prosecutors for testimony about the violence of the American Indian Movement that he said had nothing to do with whether Looking Cloud was guilty.

"This is a little man. He's a little, short man. He's disadvantaged. He's lived on the streets. He's abused alcohol and drugs. He's all alone. The United States government is on the other side," Rensch said.

"They've taken a lightning rod of prejudice ... of the American Indian Movement from the early 1970s and they've taken that lightning rod and hung it over his head."

In rebuttal, McMahon said the evidence about AIM was intended to lay the background for allegations among its members at the time that Aquash was a government spy.

"Which is why she was killed," he said.

McMahon said he was offended by Rensch's description of Looking Cloud.

"What about poor Annie Mae? What about the lady they shot in the head? What about her 8-year-old and 10-year-old daughters?" he told jurors.

"There's no hiding behind what he did. It's time to pay the price."