For such a long time, arsenic was the perfect poison.
It is odorless, colorless and tasteless, so it's difficult to detect when slipped into a food or beverage. Its effects are gradual and cumulative — deflecting suspicion from the killer. The symptoms of arsenic poisoning mimic those of other diseases common in the 19th century, such as cholera and dysentery.
Because the elemental form of arsenic occurs naturally in the environment, it is inexpensive and easily obtained. And until a clever British chemist named James Marsh devised a test in the 1830s, it was impossible to trace the poison in the human body.
No wonder Rockville resident John Parascandola dubs...