Banquillo literally translates to "bench," but in this song, it takes on a much more dramatic and metaphorical meaning. It refers to the "defendant's bench" in a courtroom.
The singer uses this imagery to express feeling accused and judged in his relationship, waiting for his turn to defend himself. This unique use of a common word in a legal context makes it particularly engaging and memorable.
El Ciego is built as a trial, and the singer is the defendant. He puts himself «Sentado en el banquillo de los acusados» (sitting in the dock), addresses the room as «Señoras y señores» (ladies and gentlemen), and pleads to a charge he does not dispute: he had her «Teniéndote de frente» (right there in front of me) and did not see her. «Cómo pude ser tan ciego para no reconocerte» (how could I be so blind I didn't recognise you) is the line the rest of the song keeps returning to.
The excuses get specific. He is always wrong and always late, and the courage is a costume: «Vestido de valiente cuando yo soy un cobarde» (dressed as a brave man when I'm a coward). He counts the loss in nights — «Me quedan tantas lunas llenas hoy vacías» (so many full moons are left to me, empty now). The chorus asks for the only sentence he wants, «Vuelve a mí» (come back to me), and the line before it leaves a question the song never answers: «Y qué hace un ciego cuando de repente ve» (and what does a blind man do when he suddenly sees).