(Need bad ending)
Important Info : When you interrogate all of them the second time you have to pin them against each other ''Mina to Arya'' Arya to Rex'' ''Rex to Mina''
At the end when everyone is arguing on who the killer is they will ask you who do you think it is. choose a random person of the 3 and they will freak out and
Continue with the game the achievement will only pop after a while it won't pop immediately i got it near the end of the game.