46. "Getting everyone's DNA on file would allow us to track down criminals and protect society."
If we wanted simply to track down criminals and protect society in the most efficient way, we would watch everyone all the time, listen in on their every conversation, constantly record all their movements, and know everything about them it was possible to know. Criminal activity would be difficult, given this approach, but no doubt clever criminals would find news ways of concealing their activities.
Even though it would undoubtedly be efficient, we don't allow it because we don't want to live in that kind of society. We want a private domain in which we have space that is only for ourselves and those we choose to share it with. The state has no business in that domain.
We treat people as innocent until proven guilty. We do not start with the assumption that all people are criminals, if only we had enough information on which to convict them. Only those who transgress the law, or who give grounds for reasonable suspicion, forfeit the right to that private space and prompt the state to enter it to protect the rest of us.
Our DNA is private information. It not only tells uniquely who we are, it can be used to tell where we have been, and in some cases what we have been doing. The state has no right to such information without good grounds for suspicion. It is more information than it can be trusted with. DNA tells even more than that, however, it tells of our genetic traits, something of our abilities and potential, and the conditions and diseases to which we might be prone. There is no way we want this information in the hands of a body we put in place to serve our interests. It would give it more power than any authority can be trusted with.