He was definitely the killer. Before Chris says anyone had died all he indicated is "Remember Dickie Moltisanti" ? The cop responds with "Listen I don't know who told you I was responsible for the death of your father" indicating that he had in fact killed Dickie because Chris never said he was dead. Than its undeniably confirmed when the cop breaks his own bannister and hides behind the couch screaming "I'm sorry" with clear indication that he did it.
No he doesn't after Chris says "Remember Dickie Moltisanti"? He says "No,Was he a friend of yours?" then after a scene with Tony talking to Bobby when you clearly miss some of Chris and the cops conversation he says "Listen I don't know who told you I was responsible for the death of your father but there informtion was either faultyor they're delibrately lying to you ". I'm not saying he didn't kill him but he didn't say what you said he did and he denied knowing Dickie or Jilly Ruffalo as you would when a gun is pointed at you.
