The problem is that, although there’s lots of due process at trial — right to cross-examine, right to counsel, rules of evidence, and, of course, the jury itself, which the Framers of our Constitution thought the most important protection in criminal cases — there’s basically no due process at the stage when prosecutors decide to bring charges. Prosecutors who are out to “get” people have a free hand; prosecutors who want to give favored groups or individuals a pass have a free hand, too.
When juries decide not to convict because doing so would be unjust, it’s called “jury nullification,” and although everyone admits that it’s a power juries have, many disapprove of it. But when prosecutors decide not to bring charges, it’s called “prosecutorial discretion,” and it’s subject to far less criticism, if it’s even noticed. As for prosecutorial targeting of disfavored groups or individuals, the general attitude is “if you can’t do the time, don’t do the crime.”
The problem with that attitude is that, with today’s broad and vague criminal statutes at both the state and federal level, everyone is guilty of some sort of crime, a point that Harvey Silverglate underscores with the title of his recent book, Three Felonies A Day: How The Feds Target The Innocent, that being the number of felonies that the average American, usually unknowingly, commits.