In the library, there's a quote by the building's namesake on one of the walls in the ground floor atrium, saying something along the lines of: "The lawyer is neither expected nor qualified to make moral judgments of his client."
It's trite. And a bit bizarre.
Why shouldn't the lawyer make moral judgments of his client? How exactly is he not qualified? I'd venture that the lawyer spends more time studying issues of right and wrong than the average citizen (certainly more than your average juror). Granted some moral philosopher can be expected to have a tighter grasp of right and wrong, and such a person would be better qualified to make the call, but the lawyer's no slouch.
The lawyer is qualified, not as qualified as some, but much more qualified than others.
Now, whether or not we should expect the lawyer to make such judgments, qualified or no, is another question. On a gut level, I don't think the lawyer is obliged to judge his clients--they are, after all, the (purported) wrongdoers, not he, and their stigma does not infect him. But nor do I think he is obliged not to make such judgments. If you know the guy is guilty, then let him fry--for God's sake don't defend him.
The typical response would be that the adversarial system brings the truth to light, that two sides battling each other to the death will produce the real story, and only then can we judge guilt and innocence. Maybe, depending on many factors. I'm skeptical.