We're going to start out this discussion with the living: civilians and unarmed enemies.
For the U.S. release, we had a couple of set behaviors for anyone who wasn't armed if gunfire went off near them or they witnessed an attack. They would run to safety, crouch and express fear. If they had no "safety zone," they would just crouch and express fear.
For the most part, our playtesters left the unarmed people alone. One person made a concerted effort to kill everyone, armed or not, but that was an anomaly.
In the final iteration of the game, there was only one civilian in the game after you received your magnum, and he is run over by a semi truck within a few moments, so very few people get a chance to try to kill him.
When we got our USK report back, one of the items discussed was that you could kill people who have expressed fear. The logic behind this being that they felt that it was inhumane to kill someone who was obviously afraid of you and was not attacking you.
At this point, we had two choices. We could take the easy road and just make civilians and unarmed enemies (like the U4 technicians) invincible. Had we done this, people who purchased the USK version would get an experience similar to other games where when they come across a civilian, they can't really do anything…the civilian is just for show. The second choice would be to make it so that civilians don’t express fear to the player.
We decided to go the second route. We did this for two reasons. First, it seemed really dumb to us to have something in the game that couldn’t be shot, especially given how important gunplay was in "SiN Episodes." Second, there was one place in U4 Labs 02 where if you were unable to shoot the lab workers, the player could be blocked from progressing through the remainder of the game.
The final result for owners of the USK version is that civilians ignore threats caused by the player. They’ll still fear mutants in cutscenes, but they no longer beg for their lives before you kill them.