4. Teresa Lewis

SOURCE

Lewis was a woman with a very low IQ, in fact, her IQ was nearly at the level of an imbecile, which complicated matters when she was convicted of hiring two men to kill her husband and stepson in 2002 in order to collect on a life insurance policy. Lewis was sentenced to death. In most instances, Lewis’ low intelligence would have made her unfit to stand trail, but she did not quite meet the threshold for lacking the intellectual capacity to be tried, and she was executed in 2010.