NORWICH, EAST ANGLIA'S bijou cathedral city, became a potential death trap this summer. Patrick Bateman wannabes had only to visit EAST International and invest in Simon Tegala's specially devised limited-edition piece, Murder with Impunity, 2000. This clearly signed, wickedly sharp, painfully trendy kitchen knife comes with a contract licensing buyers to do their worst, with Tegala committed to shoulder blame for “any indictable proceedings in relation to the Act.” His conceptual Grand Guignol practically hemorrhages issues: the artist as immoralist or redeemer; the power of money; the buying,