The roadside fingerprint plan raises serious constitutional issues that are certain to be pursued as soon as the first blue light and siren guy insists on having it done. What is the compelling state interest? How does a fingerprint check aid in traffic enforcement that a valid drivers license does not? Where does self-incrimination intrusion stop? And those are just a few that come to mind extemporaneously. As dislikeable as they often may be, the ACLU will have a field day with this one.
On the self incrimination issue. One could always refuse to comply, like many do with field sobriety tests. If you have a valid license and are pulled over for a minor infraction, what's the cop going to do? Arrest you when he already knows you are free from outstanding warrants?
Like I said, the only way this tool has any validity is with individuals with no official ID, like an Illegal Alien driving with no license.