<p><em>"The role of the U.S. Marshal is constantly changing depending on the state of the union. In the past, they were responsible for such duties as taking the census and protecting the president. In recent years, the U.S. Marshals have been responsible for "providing protection for the federal judiciary, transporting federal prisoners, protecting endangered federal witnesses and managing assets seized from criminal enterprises." We also learned that U.S. Marshals arrest more federal fugitives than all other federal agencies combined, making around 55 percent of all federal arrests". </em></p>
<p>The role of the Marshals is to track and arrest fugitives(ie: those all ready convicted and have jumped bail, or have an outstanding warrant for their arrest), and to transport them (ConAir) to the area where they are to appear to face charges.</p>
<p>They don't do the investigations. That would be the FBI.</p>