You want guarantees? Go to a graveyard, only guaranteed thing in life.
Even that is wrong, LOL. Lots of people never make it to graveyards.
Clyde, why are you drawing information from two different fiction writers? I appreciate the FBI dropping some of Douglas' work, but I am certain they have not replaced it with Ressler's fictional works, or Hunter's, LOL.
Interesting definition for serial killer that you provided. It would not fit numerous serial killers who manage to use a variety of methods/weapons to kill their victims such as Ted Bundy and Ángel Maturino Reséndiz.