A former U.S. Army captain arrested in July when he landed at Washington Dulles International Airport for stealing nearly $40 million in fuel has become a government witness helping investigators in a worldwide search for his co-conspirators, court documents said.

Lee William Dubois is expected to be sentenced Friday. Prosecutors are arguing he should receive the maximum eight-year prison term partly because he hasn’t handed over his $450,000 in profits, according to documents filed in Alexandria’s federal court.