A former defense consultant was convicted by a federal jury yesterday of conspiring through lies to a friend to funnel sensitive military procurement data to a Connecticut corporation bidding on a $100 million Marine Corps communications system.

Mark C. Saunders, the fourth individual convicted by trial in the Operation Ill Wind investigation into Pentagon contracting fraud, was found guilty in U.S. District Court in Alexandria of conspiracy, conversion of government property and six counts of wire fraud.

Thirty-four other individuals and corporations have pleaded guilty as a result of Ill Wind, which became public nearly two years ago when federal agents searched offices of consultants and defense contractors across the country.

The jury found that Saunders played a middleman's role in a scheme to pass confidential government information from George G. Stone, a Navy procurement director, to Thomas E. Muldoon, a defense consultant for Norden Systems. Witnesses said Muldoon then sold the information to Norden, which was one of 10 companies competing for a contract to design a sophisticated radar and communications system for the Marines.

Norden, one of the final four companies considered for the contract, dropped out of the competition when the Ill Wind investigation emerged.

A turning point in the two-day trial came early yesterday when Stone testified that he kept Norden in the running only at Saunders's request. Stone, Saunders's right-hand man in the Navy until Saunders left the government to open a consulting firm in 1982, said he thought he was helping his friend find work.

Stone told the jury that Saunders promised "to keep that information very closely held, that he would not release it to anybody." Testimony showed that Stone provided Saunders with information concerning each phase of the procurement's competition, including once at the 1988 Super Bowl in which the Washington Redskins defeated the Denver Broncos.

Assistant U.S. Attorney Joseph J. Aronica said in closing arguments yesterday that Saunders was not only guilty of conspiring against the government but also of violating the trust of his friendship with Stone.

"In getting the information, he also deceived Stone," Aronica told the 12-member jury. "He told Stone that he was going to use the information for his own purposes, to get a contract. Not that he was going to sell the information."

Charges against Muldoon were dropped when a federal judge said prosecutors may have filed a "vindictive" indictment against Muldoon for appealing a previous Ill Wind conviction.

Saunders faces a maximum prison sentence of 45 years. U.S. District Judge Albert V. Bryan Jr. set sentencing for Aug. 31.