Born in Svendborg, Denmark, Johnson received a Certificate of English Law from City of London College in 1968 and a Juris Certificate from the University of Copenhagen Faculty of Law in 1969.
In 1970, Johnson moved to the United States, and attended the University of Alabama School of Law and graduated with a M.C.Law degree.
Following law school graduation, Johnson started her legal career as a private practice attorney licensed in the nation of Denmark from 1970 to 1971.
In 1978, Johnson held a part-time Municipal judge for the City Court of Muscle Shoals from 1978 to 1979.
Senator Richard Shelby, Johnson was nominated by President Bill Clinton on August 31, 1998, to a seat vacated by James Hughes Hancock.