Generally speaking, its powers and prerogatives remain beyond constraint by that third branch of government, the non-secret judiciary. It is deferred to with remarkable frequency by the executive branch and, with the rarest of exceptions, it has been supported handsomely with much obeisance and few doubts by Congress.
Looking back on the violations of justice that characterized British rule in pre-Constitutional America, it is easy to see the Founders' intent in creating the Fifth Amendment. A government's ability to inflict harm on its people, whether by taking their lives, imprisoning them, or confiscating their property, was to be checked by due process.
As we are all surely aware, we now face the most ominous decisions in human history. There are many problems that must be addressed, but two are overwhelming in their significance: environmental destruction and nuclear war. For the first time in history, we face the possibility of destroying the prospects for decent existence -- and not in the distant future. For this reason alone, it is imperative to sweep away the ideological clouds and face honestly and realistically the question of how policy decisions are made, and what we can do to alter them before it is too late.