Suxamethonium chloride is a common hospital anesthetic that has, off and on, moonlighted as murder weapon.
Used to paralyze patients so that doctors can more easily put insert a breathing tube, the drug can kill very easily if the person who gets a dose of it doesn't have access to things like respirators, or a medical team. And when somebody is killed by "sux", the death can look conveniently like a simple heart attack. More importantly, writes professional chemist and anonymous science blogger Dr. Rubidium, for many years, there was no way to test for sux in a dead person's bloodstream.
Since the early 1950s, sux has been used in a clinical setting mainly by anesthesiologists. It's a mystery when it was first used in a homicide, but the first high-profile killings came in the 1966 and 1967. This salacious tale of murder involves anesthesiologist Dr. Carl Coppolino, his mistress, his mistress' husband dying suddenly in '66, Coppolino's wife dying suddenly in '67, a quick remarriage by Dr. Coppolino (not to that mistress), two trials in different states leading to different verdicts.
Coppolino's first trial in New Jersey involved a shaky witness (that jilted mistress) and a tricky toxicology problem. …
Back in the mid-to-late sixties, sux was likely considered a "perfect poison" as no tried-and-true method for detecting it in tissues was developed until the 1980s. Previous analysis had holes – including the analysis presented in both of Coppolino's trials. It wasn't sux that was detected, but the metabolites succinic acid and choline.
Her post is part of a bigger series, though. If you dig weird, toxic chemicals, you should check out the "My Favorite Toxic Chemical" blog carnival—a collection of horrifying and wondrous posts about poisons.