Well if memory serves me right, the FSD or head of security at BOS is Israeli. I believed he worked for El AL or was in some form of security at TLV airport. Therefore, I would assume that the process used at BOS is similar to the one used at TLV, but it may not be as extensive given the larger number of people that travel through BOS than through TLV on any given day.

Thus I would assume the process involves using a series of questions all looking for a/n (in)consistancy in the persons stories. They may ask the question in several ways many times. They often feed off of your answers by asking questions that seem off topic, but do provide a good idea if the person who is in front of them is honest, has been prepped or is working off a bogus background. There comes a point in questioning where the bogus story starts to fall apart. (the person does not know enough to respond naturally, and the answers start to involve a pause or more stuttering, that was exhibited before). Here is my thoughts on how the interview may go.

Security [S]: May I please see your ticket/BP and Identification.
Traveler [T]: Oh, ok. Handing over information
S: Mr. Traveler, I see that you have a MN DL and are flying down to MIA. Can you tell me what the purpose of this trip is?
T: I am a __________. And was up here on business and am going down to MIA for a meeting with a customer.
S: So why aren't you going back to MN first?
T: It was cheaper to fly direct, and I really don't feel like sitting on a plane for 8 hours.
S: So where were you working while in BOS?
T: Says where they were working. (location).
S: And where did you stay while you were here?
T: Says location
(Here is an area where a problem could come out, location of hotel not near the work location).
S: Isn't that far from where you were working? Why did you stay there and not some where closer. (This can be a false question, the hotel could be close and the interviewer is looking for the traveler to refute this, or it could actually be far away)
T: Actually, it wasn't that far away, maybe a block or two further than some other hotels. But my company tells me to stay in X chain hotel, and this was the closest to the site.
S: Ok, thanks. Have a nice flight.

In other situations. The interviewer can come back to a question you answered earlier, but change a fact in it. What he is looking for is consistancy and if you have been prepared for the questions. That is why questions will often seemingly bounce all over the place. The goal is to throw off the person who has been coached what to say. I have been asked in the interviews in TLV, after I said I was visiting friends, "Did you enjoy your time with your cousins?" Basically this was a test to see if I remembered what I had said in the past to them after they have led me down another path. Basically, I would assume BOS uses a scaled down approach to this process. In fact when I do a deposition, I often use a very similar tactic to get conflicting statements from the witness. It is very effective.