I hate to be the devil's advocate in this case, but how else would an adversarial system work? If you want to see an opposite situation, where the prosecutors have full discretion to the point that courts basically always side with them, look no further than Japan and its 99% conviction rate.
http://ideas.repec.org/p/wpa/wuwple/9907001.html
Therein is the most dangerous power of the prosecutor: that he will pick people that he thinks he should get, rather than pick cases that need to be prosecuted.
In addition to being a Supreme Court justice, Robert Jackson was also Attorney General and also the chief prosecutor at the Nuremburg trials.
The qualities of a good prosecutor are as elusive and as impossible to define as those which mark a gentleman. And those who need to be told would not understand it anyway. A sensitiveness to fair play and sportsmanship is perhaps the best protection against the abuse of power, and the citizen’s safety lies in the prosecutor who tempers zeal with human kindness, who seeks truth and not victims, who serves the law and not factional purposes, and who approaches his task with humility.
