you could detect gunshot residue on the gun found under the car in case 3 to prove this was the murder weapon
you could also test the officer for gsr to see how far away the shooter was
the arm of the sweater soaked in blood
and finally there was a bug on the vic from case 4 in the barrel
i think that is all of them
i will post a thread for the deleted scenes form the other 2 games soon