"Prosecutorial misconduct — especially the unlawful withholding of exculpatory evidence from the defense — is rampant across the country, yet prosecutors themselves are hardly ever held accountable."

That's a quote from this Cato Institute article on prosecutorial misconduct.  This is one of the dirty little secrets of the criminal justice system.  Nothing happens when prosecutors withhold Brady...

Prosecutorial misconduct — especially the unlawful withholding of exculpatory evidence from the defense — is rampant across the country, yet prosecutors themselves are hardly ever held accountable. Internal discipline does little to nothing, criminal prosecutions are incredibly rare, and — thanks to the Supreme Court’s invention of the doctrine of absolute immunity — prosecutors can never be held civilly liable, even for the most egregious, willful misconduct. This is all the more troubling because prosecutors wield enormous power in our criminal justice system, especially given the immense leverage they can bring to bear on defendants to coerce them into accepting pleas. In light of this background, it is crucial for the SJC to issue broad relief — in particular, to issue standing orders that compel pre-plea compliance with the disclosure obligations of Brady v. Maryland, and that provide for meaningful discipline and sanctions if prosecutors fail to meet these obligations.

One major problem is that there is absolutely no deterrence at all, either to prosecutors themselves for the misconduct (if you ask OPR, there has never been an intentional case and nothing even happens even when a judge finds misconduct) or to the cases when misconduct occurs (because the prejudice standard is made to be impossible). Why don’t all prosecutors have open-file, turn over witness statements and grand jury testimony, etc. It’s not because of concerns of witness safety (when is the last time something happened to a witness?); it’s because of the desire to win. The same thing for bail— why ask for detention... not because of any real fear that the defendant will run (that happens in a statistically insignificant number of cases); it’s for a desire to win. The same for arguing for monster sentences after trial. It’s done to convince people to plead. These incentives cause huge problems. 

It's not a surprise that the U.S. has the largest incarceration rate in the world.  The criminal justice system needs to be revamped to address these issues.  Until that time, we need judges to step up -- order disclosure of material (and not just say that the prosecutors know what their obligations are); grant bail (and not detain so many presumed innocent defendants); give reasonable sentences even after trial (so that the risks of trial don't result in 97.5% of cases pleading out, which means that innocent people are pleading).  And on and on.  Please excuse the rant.