Can you briefly explain this to me??

Petitioner was arrested and brought before a state judge for preliminary hearing on a robbery charge. The complaining witness testified but petitioner, who had no counsel, did not cross-examine. Petitioner was later indicted and tried. The witness had moved to another State, and the transcript of his testimony at the hearing was introduced over petitioner's objections that he was denied the right of confrontation. He was convicted and the highest state court affirmed.