AUSA is an acronym for Assistant United States Attorney. The AUSA is also known as Chief Federal Prosecutor or United States District Attorney. AUSAs represent the U.S. Federal Government in U.S. District Courts (also known as Federal Court) and Courts of Appeals.The AUSA is the legal party responsible for presenting and prosecuting a case against an individual or individuals suspected of breaking the law (or defend civil cases where the United States is a party). Their power includes initiating and directing further criminal investigations, guiding and recommending sentencing, and having the ability to negotiate “plea deals.”Therefore, a federal criminal defense attorney is a lawyer who defends an individual or individuals against the charges brought against them by the AUSA.