CALEXICO, Calif.–When he sees empty walls, Cesar Espinoza starts to picture colorful art and he immediately wants to reach for his miniature spray can to paint graffiti. The problem for this 17-year-old artist is that his passion is illegal – particularly when his canvas is private property. “Tagging,” as graffiti art is called by its practitioners, “makes me feel good because I get to express myself,” said Espinoza. He explained that his creativity expands and his art gets better on the large space of a wall rather than on a piece of paper. Many people, especially the property owners victimized by graffiti artists, might wonder who it is “tagging” their homes, fences, and even their vehicles. Sitting at a railroad crossing, one might see elaborate lettering in vibrant colors on a train’s cargo cars and wonder what the message is and who the messenger might be.