Gideon v. Wainwright
The Court ruled that the Sixth Amendment's right to a lawyer does apply to the states. It reasoned that without a lawyer, a person cannot get a fair trial. If a person does not get a fair trial, they are not getting the "due process of law" that the Fourteenth Amendment guarantees. In other words, because people have the right to due process, they have the right to a fair trial; and because they cannot get a fair trial without a lawyer, they also have the right to a lawyer.