Juicio can mean 'judgment' or 'trial', but in this context, it refers to 'sanity' or 'sound mind'. It's a key word that captures the song's theme of being
Have you ever felt so in love that you just can't stop talking about that person, even if it means talking to yourself on the street? That's exactly what Los Auténticos Decadentes and Juan Ingaramo are singing about in "Loco Perdido"! The lyrics tell us, "la gente vive diciendo que soy un loco perdido porque hablo solo en la calle como si hablara conmigo" [people keep saying I'm a lost crazy person because I talk to myself on the street as if I were talking to me].
Our singer is so smitten that he's literally walking the streets, tracing the steps of a past love, and even sitting in the bar where they first met. He admits, "yo sé que estoy loco" [I know I'm crazy], but it's a happy kind of crazy because he's so full of love. It's a fun, upbeat song about being completely, wonderfully lost in love, even if it looks a little silly to everyone else!