He filled the vacancy left by John B. Barberis Jr., who was appointed to the Illinois Appellate Court.

[3][4][5] Dugan's service on the state court bench ended when he became a federal district judge.

President Trump nominated Dugan to the seat vacated by Judge David R. Herndon, who retired on January 7, 2019.

[8] On September 16, 2020, the United States Senate invoked cloture on his nomination by a 56–40 vote.

He has been a member of the National Rifle Association of America since 2008, the NAACP since 2017, and the Federalist Society since 2017.