Important difference between fiction and reality...
Author creates "black widows" and tells the reader who they are. Author designs "black widows" to have no excuse for what they do, no alibi, no rationale, no background at all other than "evilness" [niggling PS: this is a sign, in my opinion, of bad fiction. There is no excuse for one-dimensional characters.]. In the author's world, there really is no need for judges and juries nor senates nor constitutional rights nor human rights because the author is infallible in the universe of his own creation. The author is also free to grant the power of infallible judgement to the characters he creates (see your Kip Russell quote).
We don't live in that world.