<P> The act is usually performed with a utility knife or a piece of broken glass, leaving a scar which causes the victim to appear to be smiling broadly . </P> <P> The practice is said to have originated in Glasgow, Scotland in the 1920s and' 30s, but became popular with English street gangs (especially among the Chelsea Headhunters, a London - based hooligan firm, among whom it is known as a "Chelsea grin" or "Chelsea smile"). </P>

What kind of smile does the joker have