This already goes on in Colorado for Felony convictions (not lesser charges). I believe this has been done for quite a while, but again, ONLY for felony CONVICTIONS, not arrests. Now, depending on the situation, if you are being processed, and they do a blood sample or swab for other reasons, it's already too late (though it's not supposed be held on to and used for later purposes other than for the original charges...). May we live in interesting times... :)