[1][2] Born in Montezuma, Iowa, Johnston attended the public schools in Marshalltown and Toledo before earning a bachelor's degree from Westmar College, attending Iowa State University and earning a law degree from Drake University Law School.
He then lived in Washington, D.C., and worked as general counsel for the criminal justice subcommittee of the U.S. House Judiciary Committee.
[4] Johnston's highest profile case as a lawyer was Tinker v. Des Moines, a case about the free speech rights of two Des Moines public school students who wore black armbands to protest the Vietnam War and were subsequently suspended by school administrators.
Johnston argued and won the case in front of the U.S. Supreme Court in 1969, when he was just over a year out of law school.
Persistent rumors of his homosexuality culminated in a caller questioning Johnston on a local radio talk show.