Only People Who Can Actively Use Both Sides Of Their Brains Can Solve This Case With Very Few Clues

How does the policeman know Sean is lying? - Flip For Clue 1

Flip for Clue 2

Flip for Clue 3

Sean's POV (Part 1) - Flip for Clue 4

Sean's POV (Part 2) - Flip for Clue 5

Sean's description of the murderer

Policeman calls Sean a bluff.

Here's the answer!