Ken Lammers at CrimLaw Blog has a chilling post about a person railroaded into a guilty finding in Virginia. He speaks of his disgust with what happened (essentially, someone was convicted of being an ex-con with a gun, when it wasn't clear he was an ex-con, that he had ever been convicted of a felony, when he had been a juvi in the original proceeding over a decade earlier, and where the judge and DA prevent letting the jury hear any of these facts). The defendant had actually had the store clerk where he was buying the gun call and get an assurance that the defendant was allowed to possess a firearm!
I read the story with a knowing horror. This is a prime example of the prison industrial asserting itself for the express purpose of getting convitions regardless of ethics or morality. How can they do something like this? Dunno, they do it all the time, though. The sad truth is that it is hit or miss for your typical defendant. A good prosecutor (and there are plenty) would dump this case, knowing that, even if true, it violates fundamental fairness to convict this person. A bad DA (of which there are plenty as well) would push to the hilt to give this guy 5 years in prison. Unfortunately, Ken Lammers was stuck with the latter not the former.
It's a good read, go check it out.