There's a lot of truth in what you say, however....

While obviously "we" can never be absolutely certain about the guilt or innocence of an individual even after holding a trial, I would certainly say that it's better to have a trial rather than not.

Someone has to take the responsibility for determining guilt or innocence, and I'm a lot more comfortable with the idea of a group of 12 unacquainted individuals making that determination than I am with doing it any other way.

As far as the government goes, while I would agree that some things should be kept from the general public in the interests of national security, there should always be at least ample and non-partisan Congressional oversight over this kind of thing.

I don't think it would be unfair to say that our government's intelligence arm has made enough mistakes in the past to indicate that making these determinations should not be left solely up to them.