A U.S. Marshal is a law enforcement officer who works for the U.S. Marshals Service. The USMS operates as enforcement for the federal court system, according to the University of St. Thomas at Minnesota.
The university website indicates that primary duties of marshals include protecting the safety of judges, safeguarding federal prisoners during transfer, executing the Witness Protection Program, issuing warrants and apprehending federal suspects. Federal marshals must be U.S. citizens between the ages of 21 and 36, per the site. An undergraduate degree and at least three years of professional law enforcement experience are required. Screening tools include interviews and various tests.