That's weird though, our ones in NZ use facial recognition, have to scan your passport, and then step into the booth, and look at the camera.
They don't fingerprint us though, that's some specialness I've only encountered in the US.
Off the top of my head, Singapore and Japan do fingerprints for visitors at entry as well.
Fingerprints are one of the biometrics[1] that can be stored on the chip in an e-passport, but most countries that are adding automated border control today use facial recognition since photos are universal.
1. Photo, fingerprints, and iris scan. Relatively few countries add fingerprints and I don’t think any country adds iris scans.
ID cards are another matter, but I didn’t include them because most national ID cards can’t be used as international travel documents.
This is tangential to the topic of immigration clearance but my Singapore ID literally has my thumbprint printed on it, which I’ve always found hilarious.
Maybe the biometrics on my passport were sufficient already? NZ tends to be an early adopter of such things, as we make a great place to trial new tech, small market unafraid of new shiny.
It was rather amusing, in a shameful way.
Personally I use them 2, maybe, 3 times every trip before queuing up again to have my passport checked manually. :P
Obviously other countries have their own rules.
The best example I can find is https://en.wikipedia.org/wiki/William_Worthy#Right_to_travel...:
“He was able to return to the U.S. in October 1961, showing his birth certificate and vaccination record at Miami Airport”
That’s decades ago, though, and he still showed something (but not something that realistically identified him) to get in.
You can show them any identification documents you do have, like drivers license, to establish your identity. For establishing citizenship, one option is if you previously has a passport (expired, or just not with you) then can look up that record, and if it is recent enough to pull up a photo they can compare to you that can also help.
Other ways of verifying citizenship depends on what databases they have access to. For example if they have access to the Social security numident database, they could look up a number to see the associated name citizenship flags. I'm not sure if they do though.
From what I have heard anecdotally is that it is usually not too hard to convince them if you really are a citizen (except in edge cases like being born abroad to Americans without parents registering your birth with the US.)
In any case they will formally warn you about it being illegal for Americans to enter without a passport (it is, but there is no punishment for the crime anymore). This is to deter you from doing this again in the future, as having a passport makes things much faster and easier for everyone.