Originally Posted by
FlyingHoustonian
Normally you should hand your declaration form over to the Customs agent as your are departing the baggage claim area (after immigration)
That form has your trip details (at least what you choose to write) and length on it.
I'm looking at the CBP declaration right now, and as I thought, the only trip details you fill in are a) countries visited; and b) flight #.
Unless Immigration writes the trip details in the "For Official Use Only" section at the bottom (I've never looked to see
what they write there), the customs official wouldn't know anything besides where you've traveled. I'm sure they could pull it up on their computers for questioning, but IME, the CBP agents never type anything into a computer when I hand them the form -- they just take the form from me, give it once-over (sometimes not even that), and then wave me on. I doubt they know anything about my trip besides where I've been when/if they decide to do further questioning.