COACHELLA, Calif. -

A man hired to advise the Twenty-Nine Palms Band of Mission Indians is the third person to plead guilty to federal charges stemming from a scheme in which hundreds of thousands of dollars were kicked back to an attorney for the tribe and his wife, prosecutors announced Tuesday.

The tribe operates the Spotlight 29 Casino in Coachella.

David Alan Heslop, who was hired by the Coachella-based tribe to oversee some of its business enterprises, pleaded guilty Monday to conspiracy to commit bribery for paying hundreds of thousands of dollars in bribes to Gary Edward Kovall, general counsel for the tribe, according to the U.S. Attorney's Office.

According to court documents, Kovall and Heslop formed companies, and the attorney ``convinced the tribe to award construction and consulting work to those companies. To disguise Kovall's interest in those entities, Heslop paid Kovall's share to Peggy Anne Shambaugh,'' Kovall's then-girlfriend and now wife, according to the government.

Over about 18 months ending in mid-2008, the tribe paid the companies about $2.8 million. Heslop then paid Shambaugh about $300,000 ``to influence and reward Kovall,'' according to prosecutors.

Kovall, Heslop, Shambaugh and Paul Phillip Bardos, a general contractor from Rancho Cucamonga, were charged in a 48-count grand jury indictment in May 2012.

Bardos, who did or subcontracted much of the construction work awarded by the tribe, admitted depositing income he earned into his personal checking account, concealing the money from his accountant, and not reporting it on his tax returns, according to federal prosecutors.

Kovall, who's from Minnesota, and Bardos both pleaded guilty last month - Kovall to conspiracy to commit bribery and Bardos to tax evasion. 

Heslop, 76, of Templeton in central California, is scheduled to be sentenced on June 30 and Kovall and Bardos on Sept. 29. All three face up to five years in prison.

Shambaugh is being evaluated for a program in which she'd be supervised by a court officer for a period of time, and if she complied, the charges would be dismissed, according to federal prosecutors.