During the "Smash the State" sidequest (2nd time in Detroit), you will be asked by your old friend Nicky to track down a guy (Jacob White I believe) who is running around with some explosives. You will find Jacob in the sewers underneath the Police Station.
WARNING: Jacob has mines set up in the sewers, so move slowly!
Anyway, once you take care of this crazy bastard, you will find a weird looking device with a keypad on it. Enter the code "0000" and this trophy will pop.