Question from a reader: I need a fatal poison for a 105-lb. woman that begins acting in 20-30 minutes and the victim dies shortly thereafter – within an hour. Just after ingesting the poison in an alcoholic drink, the victim needs to be physically able to walk or stagger to a nearby subway stop, take a 5-10 minute ride to Grand Central, and then get on a commuter train. She’s found dying on the train after it leaves the station. Cyanide and Strychnine both seem to work, but the newer prescription medications don’t. I’m a rank amateur at this. Would you be able to suggest a suitable poison?
Cyanide would do it (remember the Tylenol murders?). Speed of onset is dose-dependent. The victim would feel “general weakness, giddiness, headaches, vertigo, confusion, and perceived difficulty in breathing. At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the person progresses towards a deep coma, sometimes accompanied by pulmonary edema [fluid in the lungs], and finally cardiac arrest. A cherry red skin color that changes to dark may be present …”
Basically, cyanide causes the body to be unable to use oxygen. There may be plenty around, but the cells can’t use it. This is a reasonably good reference if you want more info Cyanide Poisoning.
Note that sugar inactivates some of the cyanide so maybe don’t mix it in a daiquiri…and it smells like almonds, so something like amaretto would mask it nicely.
Strychnine would be less appropriate for your story as the victims are in a lot of pain and have muscular contractions that would be visible and garner attention on the train. Also, the onset is probably too fast.
Arsenic would be too slow for your purposes here.
Digitalis (digoxin) toxicity is another option, but it’s onset is a couple of hours so she’d need to be at the bar for a while before she heads out. If you want more info about that, let me know.