In Saw Zep Hindle was told he had to kill a mother and her child to get the antidote or else he would die. He hadn't much of a choice then but becoming a murder, but Jigsaw always said he doesn't approve murder so what happened there? What was Zep supposed to do before Jigsaw's eyes then? If he really was supposed to commit murder, then how is this reconcilable with Jigsaw's views on murder?
Five months later Zep was abducted by the Jigsaw Killer, whom he didn't know was actually John Kramer. John poisoned him and left him a tape which provided instructions for Zep and told him that in order to get an antidote which could save his life he had to kidnap Alison and Diana Gordon, Dr. Gordon's wife and daughter, and had to hold them hostage while Gordon was forced by Jigsaw to play a game on his own. Furthermore he had to kill Gordon's family if the latter didn't pass his test by killing his cellmate, Adam Stanheight, by six o'clock.
I would wager that Jigsaw was expecting Gordon to kill Adam. This way, Zep would not have to kill anyone, just hold them hostage and then release them. Unless the Gordon family was guilty of something, there would be no point in killing them.
However, there's also the option of an ill-conceived plot point...