I’ve heard of historical cases of people dying by poison being applied to fabric, accidentally or deliberately. Is contact poison a viable method of murder? Could it be used, not to kill altogether, but to weaken an opponent for someone else to fight?
It depends on the poison. There are a lot of poisonous substances that can be absorbed through the skin, including things like Anthrax, Strychnine and Cyanide. (Technically Anthrax is a biological agent.)
There are poisons that can disorient or impair the victim without killing them. Too many to even start to go into them.
Ironically, the first thing that comes to mind and fits both of these is Lidocaine. Lidocaine, and a number of other similar anesthetics such as Novocaine and Oracaine, are synthetic relatives of cocaine, producing numbness on contact, and they’re commonly used in dentistry. You can kill someone with a sufficient dose, as well. Also, the normal topical administration method is via a gel, not a liquid but the idea is there.
One major, historical, issue with accidental poisonings was arsenic. When used as a dye, Arsenic produces a vibrant green color. This was briefly popular in the 18th century, for wallpaper patterns and paints. In a dry environment, it’s mostly safe, however when you add heat and humidity, low doses can be released as an (effectively) undetectable vapor. This won’t result in an immediate death, but prolonged exposure can result in chronic poisoning.
There’s a bit of history here, if you’re interested: In 1815, after his military defeat, Napoleon Bonaparte was sent into exile on the Island of Saint Helena. He’d previously been exiled to Elba in 1814, after a separate military defeat, only to return to France, and restart his campaigns, so this time he was sent to a far more remote island. Six years later, on May 5, 1821, he died.
Napoleon’s autopsy listed the cause of death as stomach cancer, there were ulcers found during the procedure, and a family history (though that wasn’t, apparently, known at the time). And, that was that… until the mid 1960s.
This is where things get a little strange. Records kept, both before and after Napoleon’s demise, suggest that he may have died from chronic arsenic poisoning. This includes the symptoms he displayed as his health deteriorated on Saint Helena, as well as how well his body was preserved when it was eventually moved from the island to France in 1840. Additionally, surviving hair samples displayed arsenic traces one hundred times what you would expect today. (The biology involved is that, because arsenic is an element, it doesn’t break down in the body, so it is flushed through various sources, including your hair.)
Into the early 2000s, there was a persistent theory that, because he’d managed to escape Elba, the British had decided to finally finish him off (St. Helena was a British holding). Politically, they couldn’t simply execute him, so the theory held that they dosed his private wine stocks with low doses of arsenic.
The competing argument, of course, is that his wallpaper used an arsenic derived green dye, and that the elevated arsenic content found in the surviving hair samples was the result of atmospheric exposure, probably throughout his life, but particularly during his time on St. Helena.
I am skimming over a lot of details here, there are entire books on the subject of Napoleon’s exile to St. Helena and his eventual death, and rumors that the British were poisoning him, or plotting to kill him existed at the time. So, at some levels, this is nothing new.