Yes, it is a very good thing to have in place since it makes it a whole lot easier to solve a crime if we have the dna of a whole lot of people there and on file so that we can see who might have done the crime then.
I don't see any reason why a DNA database of criminals would be consider unconstitutional, it does not break any of our rights in the Bill of Rights, I think that if it was a truly unconstitutional thing you would be seeing people bring this issue up for the Supreme Court to decide.
Yes, a criminal DNA database is constitutional, because the person has to have had to commit a crime in order to be put in a database. If we were all just put in the database, that would not be constitutional. But once you commit a crime, you lose some freedoms. It is a small way to keep track of dangerous people.
DNA technology is a "brave new world" that we are only now getting used to, and it prompts many new issues in law and society. The US government has no right guaranteed by the constitution to capture information at this level; I believe this is an area that is too far afield for us to guess what the framers intended. New law must be created and perhaps the consitution should be amended.
I do not believe a criminal DNA database is constitutional. I don't trust my government to hold mine or any ones DNA information. I find this to be a huge breech of privacy. Secondly the plan make me question how long the government would wait before they declared they were going to keep a record of every persons DNA.