Via Douglas Berman at Sentencing Law & Policy, a scholarly article by Lawprof Stephanos Bibas of Penn Law School and formerly an AUSA in the Southern District of New York, seeks a mechanism to assess prosecutorial discretion:

Prosecutorial discretion is a problem that most scholars attack from the outside.  Most scholars favor external institutional solutions, such as ex ante legislation or ex post judicial and bar review of individual cases of misconduct.  At best these approaches can catch the very worst misconduct.  They lack inside information and sustained oversight and cannot generate and enforce fine-grained rules to guide prosecutorial decisionmaking.  The more promising alternative is to work within prosecutors' offices, to create incentives for good performance.

Always an issue with criminal defense lawyers, who harbor the belief that there are far too many prosecutors who take advantage of the fiat of their position despite our claims of the blindness, the injustice, the harshness of their attitude and approach.  Given that charging and plea authority in the hands of young prosecutors is the most significant factor in determining the parameters of the outcome of a prosecution, short of a total acquittal, it's hugely significant that prosecutors exercise discretion appropriately.

But that's not what caught my eye.  This did:

A better solution is to collect and aggregate feedback from a variety of sources, including peer prosecutors, supervisors, judges, defense counsel, victims, defendants, and the public, as eBay does.  This information, appropriately weighted and discounted, could better encourage prosecutors to serve all their constituencies.

Few of us have given sufficient thought to eBay as the model for assessing the criminal justice system.  Don't scoff.  You never know where the next great idea comes from.

I can see it now, click on the docket number and check out the crime.  The outcome of the case can replace the price on the feedback page, unless of course there actually is a price (which could present other issues).  And then the comment. 

Great prosecutor, gave deft 5k1 for nothing.  Coop was total crap! AAA++++

The AUSA can have a feedback score, with little colored stars to show how many defendant's he's covered.  But not all feedback will be positive, of course.

Jerk, coerced 121 months b/c co-D flipped & lied. Do Not Use This One!!!!!!!

Of course, it's not like you can pick your prosecutor, so the system may have a flaw in that regard.  And what about a Rule 35 motion, where a miserable plea ended up with a decent cut in sentence after the fact?

Feedback withdrawn by mutual consent

That could raise some eyebrows on the street. 

The system requires that a degree of discretion reside in the hands of prosecutors.  The fairness, propriety and utility of the criminal justice system depends in large measure on how they exercise this discretion.  Many prosecutors are young, naive and deeply sheltered from reality.  This isn't a fault, but a fact.  One can only expect so much understanding from a young person who has just emerged from law school or a clerkship and has been given people's lives to play with.

While the eBay feedback system raises fun images in my mind, particularly given how much I enjoy eBay to find those antiques I so love, I don't imagine any feedback a defense lawyer might leave will have much of a positive impact on a young prosecutor.  As for judges, it would be my hope that they might express their thoughts during the course of the prosecution rather than wait until afterward to play a role. 

I can't imagine any defendant being satisfied with learning after the fact that the shipping cost was too high.  And whether or not the description was accurate will inevitably be a product of outcome, hardly a good way to judge the exercise of discretion.