Over the past few centuries, arsenic poisoning has been a particularly popular way to kill someone. It's odorless, tasteless, and builds up in the human body. A large dose will kill someone in hours, while a steady, small dose will cause someone to become ill and appear to die from natural causes. The poison used to be extremely difficult to detect after death, until James Marsh developed a reliable test in 1832. Even after that, only the victims of suspicious deaths were tested—so many arsenic killers tallied up multiple victims before being caught. Read about a few of them in an article I wrote for mental_floss. The original title was 13 Women and Their Arsenic Habit, lest you think I'm losing my touch.