Bill was born in Gulfport, Mississippi and graduated from St. John High School in 2002. He obtained a Bachelor of Science in Forest Resource Management from Clemson University in 2006, and in 2009, he graduated from the Mississippi College School of Law. During law school he interned with the Federal Public Defender in Jackson, Mississippi. After law school, Bill opened a law firm with his father, former federal prosecutor Peter Barrett, practicing mainly in the area of federal criminal defense. In 2011, Barrett was selected to join the Criminal Justice Act (CJA) Panel for the Southern District of Mississippi. As a member of the CJA panel, Barrett represented numerous clients in federal court appointed cases, both at the trial level and in the Fifth Circuit Court of Appeals. In 2014, Barrett was selected as the CJA Panel Representative for the Southern District of Mississippi. In July of 2015, Barret was sworn in as an Assistant District Attorney for the 19th Judicial District.