Brain Fertilizer

Are there some situations in which it is a waste of time to attempt to ensure a fair trial?

I mean, every time I try to think of a situation in which a person could be slam-dunk convicted enough that we don't really need to offer them a trial in order to bring about justice, I think of the movie F/X. Sure, someone can be framed even in our legal system, but a trial at least provides a chance for intelligent people to try and find minor flaws and inconsistencies that might indicate the appearance of guilt is due to a frame attempt. I always conclude that we are better off with things the way they are.

But what about Saddam? I really think that if we merely grabbed and put him up against a wall and shot him without another word, it would still be justice. In fact, the only injustice might be that we could possibly miss out on a full accounting of his atrocities...maybe.

Is it worth the risk of a successful escape or rescue or an intimidated jury to actually put him on trial? Regardless of the issue of determining his guilt/innocence, is the benefit more just in allowing the new government to confront, accuse, and execute him for the potent symbolism involved?

The only reason I'm asking is because if there is even one definitive circumstance in which we can say that there is no need for a trial, then we should consider that in light of our legal system, and see if there would be any way to safely implement and even expand the circumstances in which a person may be convicted without a trial, in the interests of justice. Could top-notch DNA analysis ever provide the necessary accuracy required (such as being able to not only identify the person through DNA, but also able to tell when the DNA had been planted by pouring a vial of bodily fluid after the fact)?

Lawyers and law students, specifically, are invited to weigh in.

UPDATE:
I'm not saying Saddam is our responsibility, just that his crimes are well-documented enough that Iraq doesn't really need to try him. If any case can be said to make a trial unnecessary, I'd say it was this one. (Or Hitler's...but Hitler is still living in Argentina or Bolivia, and so outside the scope of our discussion) So, if Saddam doesn't really need a trial to establish his guilt, is there any possibility of any case in the United States legal system in which we don't have to assume innocence before proven guilty? If not, well, then question answered, end of story. But if so, what are the circumstances? And would it be advisable or even possible to adjust our legal system toward that direction at all?