Jimmy Thomas Sasser stood in silence in February as a federal judge sentenced him to four years in prison. For more than a decade, prosecutors said, Mr. Sasser, an insurance adjuster from Wilson, N.C., participated in a plot involving dozens of farmers, warehouse workers and insurance agents who conspired to defraud the federal crop insurance program of nearly $100 million by claiming fake losses on crops. Prosecutors said Mr. Sasser had taken kickbacks of $400 to $2,000 to falsify claims, and he was ordered to pay more than $21 million in restitution.