Well, we know the doorman was wrong about something, because lulu had to have walked in the door sometime. So he either does not watch the people or he does what I mentioned, that is, looks who is coming in but if busy & doesn't look exactly who they are, and does not say anything if they look like they belong. If the first one, then that is a serious breach and I hope there are video cameras backing up who comes in and out because I would hate the defense to use the doorman missing them as an opportunity for them to argue, "if the doorman missed them maybe he missed the "real" killer coming to the luxury apartment at 5pm to murder 2 children without motive." I would just hate for that gap to even give the chance for the defense to argue reasonable doubt. Perhaps that is why DA is talking to this guy.
If the second one, unfortunately I think some doorman do that. And if there is not a backup porter or concierge then if they are out hailing cab or helping someone else, there is a gap in airtight security bc they may not notice who exactly comes in. A nanny w 2 kids fits in. A nicely dressed reporter fits in, and if she or he confidently strutted in the building acting like she or he belonged, a timid or busy doorman might not stop them. I would be a little upset that it is now advertised all over NYC that the doorman on this building may not be that careful and that he does not notice who comes in and out. I doubt anyone else in the building would let a reporter in their home, maybe they would meet in the lobby, but their actua apartment? Seems odd too the doorman would not know exactly, oh, they were going to apartment 8g or something? Instead he gave a vague answer.