History of Joker’s “Glasgow Smile”:

“The Glasgow Smile, also known as the Chelsea Grin, is a form of torture that was originated by various gangs living in the Scottish city of Glasgow, and soon become popular with criminals headquartered in Chelsea, London. It’s primarily meant as a calling card – a warning to other gangs to back off or this is what will happen to you. It is also employed by bookies whose clients welch on bets.

Basically what it is, is a cut starting from each corner of the mouth and stopping just short of the ears. In old times knives were used for this effect but in more modern times, the mobsters hold the person down and insert a credit card lengthwise into the person’s mouth to keep the mouth open. The cuts form scars resembling a grin. Afterwards, the victim may be kicked and stomped on repeatedly in order to make them yell as that in turn will rip the flesh more and widen the grin. The victim of a Chelsea Grin may indeed bleed to death in some cases.”

Source Commenter “Takerrocks5” on ign.com