Judge Johnson was an Associate Judge, Montgomery County Circuit Court, 6th Judicial Circuit, from August 2000 to October 2014. He has presided over jury trials including serious criminal cases, complicated civil cases, family law cases and both criminal and civil motions. Mr Johnson prosecuted serious criminal cases, and represented civil and criminal clients. He served on the District Court for Montgomery County, Maryland (1996-2000). He also served as a police instructor at the Montgomery County Police Academy (1981-1987).

He was Adjunct Professor University of Maryland, University College (1990-2011), teaching Criminal Law and Procedures, Strategic Plan Homeland Security, Law Enforcement Administration, Criminal Courts, Race Crime and Criminal Justice, Criminal Courts, Immigration Law: Deportation, Correctional Administration, Law of Corrections, Juvenile Delinquency, Victimology, History of Drug Use in America, Landlord Tenant Law; Psychology of Criminal Conduct, Internship in History, Contemporary Criminological Theory, Criminal Law in Action.