Your poison ivy super-nerd was watching a 1944 movie with Edward G. Robinson, who gets caught up in a murder situation…
At one point Robinson is riding along with the Police investigator who wants to know where Robinson got that nasty poison ivy rash!
Interesting to me was that they never showed his hand where the rash was supposed to be obvious; not sure why. The movie was directed by the great Fritz Lang, who grew up in Germany and probably didn’t relate to concept of poison ivy.
There is a scene in the woods where the body was dumped and the police had placed a wooden palette over a plant that they said was poison ivy, although you couldn’t see the leaves. Poison ivy doesn’t grow in California; only poison oak, which looks similar enough that they could have used it.
But on a much more grisly note, I got a call a few years ago from a fellow wanting to know how long after exposure the poison ivy rash shows up. He was on trial for killing his wife and dumping her body in the woods in a patch of poison ivy. It was extremely creepy talking with him, and from what I read, it was pretty clear he did kill her, and went to prison for it, eventually. This was by far, the most bizarre poison ivy related incident I have ever experienced.