Betts v. Brady
In their decision, the Court did rule that there were special cases where a court should assign a lawyer.  In these special cases, not having a lawyer would make it difficult for a defendant to get a fair trial.  In each case, the judge was supposed to talk to the defendant to figure out whether any of these "special circumstances" existed.  For example, was the defendant mentally able to defend himself?  Did he have enough education?  Did he understand what happens during a trial?