Fourteenth Amendment, Section 1:
All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
A convicted defendant may not be imprisoned solely because of his indigency. Williams v. Illinois 1 held that it was a denial of equal protection for a state to extend the term of imprisonment of a convicted defendant beyond the statutory maximum provided because he was unable to pay the fine that was also levied upon conviction. And Tate v. Short 2 held that, in situations in which no term of confinement is prescribed for an offense but only a fine, the court may not jail persons who cannot pay the fine, unless it is impossible to develop an alternative, such as installment payments or fines scaled to ability to pay. Willful refusal to pay may, however, be punished by confinement.