I read the other posters concerns about Fourth Amendment protections as responding to the surveillance use, not to the collection. My post was in response to my general read of those concerns.
It seems your objection is primarily to the collection of the voice print itself. Why do you feel like that's different from collecting finger prints?
Fingerprints are harder to use in electronic mass surveillance.
Databases are easy to combine, the only barrier is often just a legal one (which is a joke for national security). So I'd like governments to collect as little of that data as possible.
+1 to you, sir. Having inmates train the voice recognition is (in my opinion) compelling an admission.