[2] He is the son of Mike Duncan, an attorney who is a former Chair and current member of the Board of Governors of the United States Postal Service and former Chair of the Republican National Committee.
After law school, Duncan served as a law clerk for Henry Rupert Wilhoit Jr. of the United States District Court for the Eastern District of Kentucky.
Serving as an Assistant United States Attorney, he prosecuted complex drug trafficking, money laundering, firearms offenses, and violent crime.
[7] Duncan was nominated for United States Attorney for the Eastern District of Kentucky by President Donald Trump on August 3, 2017, confirmed by the Senate on November 9, 2017, and was sworn in by Karen Caldwell, Chief Judge of the Eastern District of Kentucky, on November 21, 2017.
[9] It February 2021, it was announced that Duncan would enter the private sector becoming a partner at the Dinsmore law firm in Lexington, Kentucky.