Situation:
Bob and Carol and Ted and Alice all live in the same house. Bob and Carol go out to a movie, and when they return, Alice is lying dead on the floor in a puddle of water and glass. It is obvious that Ted killed her but Ted is not prosecuted or severely punished.
Possible solution:
Bob and Carol are humans as we expected but Alice is a goldfish and Ted is a cat. So, cat Ted ate goldfish Alice.