Long time ago, in college in the 70's I was in the library reading a chapter in a book written for fire investigators. Was a slow day. It cautioned that just because you find some badly charred and burnt wiring, it doesn't mean that it caused the fire. That a fire caused by something else will likely get to and find some wire that was in good condition and damage it. And that damage may assist the fire further, but it can't be blamed as the initial cause.
