CSI, the hit crime drama series, has misled audiences into thinking that crimes are solved easily and quickly. In fact, many murders (and other crimes) go unsolved, more than you think, about 40%, according to the FBI. Some of the unsolved cases have gained notoriety, partly because of their gruesome nature, partly because of newspaper sensationalism, but always because they went unsolved. Nothing is more unsettling than thinking there is a serial killer on the loose in your town. Here are 5 of the most famous unsolved murders in history.