In 1994, Swinson returned to his home base of Washington DC, where he joined the Metropolitan Police Department. Swinson began his career as a police officer in uniform. He was then assigned to the Gun Recovery Unit as a tactical officer. Shortly after that, Swinson was assigned as a plainclothes/undercover officer, targeting narcotics and crimes in progress. In 1998, Swinson was assigned to the Third District Detectives Office as an investigator, where he covered offenses ranging from burglary and armed robbery to homicide. In 2000, he was promoted to detective and was eventually assigned to the department’s Special Investigations Bureau/Major Crimes, and was the lead investigator in the District of Columbia for investigating serial burglaries, high profile cases and organized criminal operations related to narco-fencing.
After retiring from the police department, Swinson began writing crime fiction. A Detailed Man came out in 2011 followed up with The Second Girl, the first book of his Frank Marr trilogy.