Retinal and fingerprint scans?

Can someone explain to me how you're going to do retinal and/or fingerprint scans at our borders? As a computer professional, I realize that for these checks to be worth anything, you have to have a database with existing exemplars in order for it to be useful. How in the name of God are you going to have existing exemplars for all the illegal aliens pouring across our borders? I guess Kerry will deploy the ESP squad to take the exemplars in Mexico and Guatemala and Chechnya and Iran and Syria and, and, and, and so we can be ready when they show up.

Sheesh!