PIERRE, S.D. (AP) – A federal jury convicted Crow Creek Sioux Tribal Chairman Duane Big Eagle Sr. on bribery and conspiracy charges Thursday for his role in a scheme that rewarded tribal officials for giving construction companies contracts for new buildings at the tribe's school in central South Dakota.

The jury found Big Eagle, 61, guilty on two counts of conspiracy to bribe a tribal official and one count of bribery involving an agent of a tribal government. It acquitted him on one count of bribery.

Big Eagle declined to comment after the verdict Thursday, but his lawyer, Dana Hanna, said Big Eagle will ask a federal appeals court to overturn the convictions.

“Of course I'll appeal,” Hanna said.

U.S. District Court Judge Roberto A. Lange set Big Eagle's sentencing for Oct. 24, when he could face to up to 20 years in prison.

The charges relate to tribal officials' actions in awarding a $3.5 million contract to build a new dorm and kitchen facility at the tribal school after a 2005 fire destroyed the previous building and awarding other contracts in 2008 to build housing at the school. Other tribal officials and contractors have already been convicted for their roles in the scheme, which involved contractors giving tribal officials thousands of dollars in bribes in return for receiving contracts.

Big Eagle has been chairman of the tribe for 13 of the past 19 years, according to prosecutors. The tribal council also acts as the school board on the reservation.

In closing arguments to the jury earlier Thursday, federal prosecutor Carl Rostad said Big Eagle should be convicted because evidence showed he joined other tribal officials and contractors in a system of corruption that stole federal money that should have been used to benefit the tribe.

“Ladies and gentlemen, the cycle of corruption doesn't end until all the people are held accountable,” Rostad told the jury. “Duane Big Eagle should be held accountable.”

But Hanna, the defense lawyer, argued that prosecutors failed to provide reliable evidence that Big Eagle knew any payments were bribes. Big Eagle should be acquitted because the main evidence against him came from two people previously convicted in the case, and those two admitted they had lied about some aspects of the case, he said.

“I submit to you a perjurer's testimony, both of these guys, should be rejected entirely,” Hanna told the jury.

Big Eagle did not testify at the trial, which began Monday, but his defense lawyer said Big Eagle told his side of the story by pleading not guilty.

Rostad said tribal officials would pay contractors, who then would give cash to the tribal officials. Former school superintendent Scott Raue, who is now serving a prison term for his role in the scheme, received payments from a contractor in 2005 and then split the money with Big Eagle and others, he said.

“That's how corruption works. You give a check to the contractor. The contractor deposits it and gives you back your cut,” Rostad said.

Lester Thompson, who was elected tribal chairman in 2006, and Brandon Sazue, who became chairman in 2008, broke the cycle of corruption by telling federal officials what was going on, Rostad said. When Big Eagle was chairman, before 2006 and after being elected again in 2010, he never told federal officials about any corruption because he was part of it, the prosecutor said.

Hanna said Raue and Norman Thompson, a former tribal official, presented the main evidence against Big Eagle, but their testimony should be rejected because they are convicted felons who have lied about the case.

Prosecutors also presented evidence from a 2008 meeting, taped secretly by Sazue, in which a contractor wrote a $5,000 check to Big Eagle, who then cashed it. Big Eagle kept $1,000 and gave $1,000 each to four other people, according to prosecutors.

Hanna said the tape does not show Big Eagle was part of any crime. Big Eagle would never have cashed the check and created evidence against himself if he thought it was bribe money, the defense lawyer said.