Jack Ruby described what Officer Roy Vaughan and Lt. Sam Pierce were doing at the head of the ramp. He said that Vaughan (although Ruby didn't know his name) was leaning into the car and talking to Sam Pierce (whose name Ruby knew).
Since there was a crowd there, and Vaughan's assignment was to keep people out, how long would he take his eyes off the ramp? But, the way it was put to us, and the way it was shown in the tv movie Ruby and Oswald, is that Vaughan was helping Pierce exit onto Main Street, that he moved forward to the street to uphold the traffic so that Pierce could get out. And you see that happen in the movie. But, Ruby didn't say anything about that. He just said that Pierce was stopped, as in parked, at the head of the ramp, and that Vaughan was talking to him.
Again, at a time like that, when Vaughan had the crucial assignment of making sure no one entered, how long would he diddle with Pierce chewin' the cud? What did they have to talk about?
Pierce: You keepin' people out?
Vaughan: Yeah. Nobody's getting in here on my watch.
Pierce: Good. You doing alright? How's the family?
Vaughan: Ahh, mostly all right. My kid has got an ear infection, but, you know, it happens.
Pierce: May that be the worst thing that ever happens to him. By the way, what are these people doing here? This is an incoming ramp. Is there someone they're expecting?
Vaughan: Beats me. I have no idea. People: they're the worst.
Pierce: Tell me about it. Well, I guess I better head out. Time's a'wasting. You stay sharp.
Vaughan: As you say, Sir.
Let's remember that Ruby saw and recognized Pierce. And Pierce knew Ruby. So, doesn't it seem likely that Pierce would also recognize Ruby? Was this really a situation in which both Pierce and Vaughan were tuned out, that is, tuned-in to each other, such that they missed seeing Ruby? Why would anyone not have doubts about that? This was a police operation, a high-intensity "secure the zone" operation. Aren't police supposed to be disciplined? Aren't they supposed to be thorough? Aren't they supposed to be highly observant? Again: this is something that an 80 year old Walmart greeter could have done. But, two cops couldn't?
Joseph Backes says that the Dallas Police were complicit with Ruby, that Fritz positioned himself to give Ruby an opening to get to Oswald. Well, in that case, isn't it reasonable to assume that the Dallas Police let Ruby into the garage? Why would Fritz leave an opening for Ruby to get to Oswald without first leaving an opening for Ruby to get into the garage? So, even the Idiot Backes has every good reason to believe that Vaughan and Pierce allowed Ruby to enter.