Final answer:
Clarence Gideon was jailed for breaking into a poolroom and stealing, but his case led to a landmark Supreme Court decision ensuring the right for legal representation for all felony defendants.
Step-by-step explanation:
Prior to the Supreme Court case Gideon v. Wainwright, Clarence Gideon was in jail because he had been convicted of breaking and entering a poolroom with the intent to commit a misdemeanor theft. Unable to afford a lawyer and being denied a public defender by the court, Gideon represented himself and was subsequently found guilty and sentenced to five years in prison. In prison, Gideon drafted a handwritten appeal to the Supreme Court, leading to a landmark decision that established the constitutional right for felony defendants to have legal representation provided at the state's expense if they cannot afford one.