I'm a murder mystery writer and recently I came up with an interesting idea for a murder method, but I was curious in particular legal logic behind it.
Let's say two adults - Persons A and B - decided to shoot their BB guns at the other, for some reason. Unbeknownst to Person A, a third party hours prior - a Person C - replaced A's BB gun with an actual gun that looked exactly like the original BB gun. When Persons A and B shoot at each other, B of course dies.
Let's say later, in the course of the case, it was proven beyond a doubt that Person A didn't know he had an actual gun. On top of that, it was conclusively proven that Person C was the one who switched the BB gun with an actual gun. Would Person A still be convicted or face some sort of legal trouble? Additionally, would Person C ever be arrested, even though he technically wasn't the one who killed Person B?