Simple solution: dig up the corpse and use Touch ID. :P
LOL!
Nice idea, except for two problems.
1: The TouchID requires a living finger to work. It will not work with a dead finger. For example, you cannot cut of the finger of someone and have it unlock their iPhone.
2: The iPhone 5C doesn't have TouchID at all. It was the iPhone 5S's poorer cousin, which was sold without the features of it's fancier cousin.