For those unfamiliar with the system, it may come as a surprise to learn how crimes are prosecuted in American courtrooms. Prosecutors have the power to choose to prosecute or not prosecute crimes. They have almost unchecked authority to make decisions that impact people's lives profoundly. Many prosecutors take their authority seriously and do their best to further the interests of justice in executing their duties. Unfortunately, there are prosecutors who abuse their power. In those cases, there is almost no oversight and little ability to address instances of misconduct.
Prosecutors are elected. On the surface, this might appear to be a check on misconduct or incompetence. In reality, few voters have the incentive or the opportunity to understand how an individual prosecutor is performing. The most an enthusiastic voter might learn is whether a prosecutor has a "good" win-loss record. That is nothing more than an incentive for prosecutors to pursue victories at any cost, even the cost of justice.
Appeals are one way to address mistakes and misconduct committed by prosecutors, but they are not ideal for that purpose. If a case is overturned on appeal, prosecutors do not suffer penalties. In fact, even proof of misconduct by a prosecutor can be ruled a "harmless error" and allow an appeals court to uphold the conviction. There is no penalty, not even an unfavorable result in the case, for prosecutors who commit some forms of misconduct.
Justice should not be dependent on the positive intentions of individuals. Oversight is necessary to ensure that the process is free from bias, foul play and incompetence. In the absence of oversight, prosecutors have the power to turn the criminal justice system on its head. The rules that are meant to ensure fairness are meaningless if the parties involved are not required to follow them.
Source: The Daily Beast, "How to Hold Bad Prosecutors Accountable: The Case for a Commission on Prosecutorial Conduct," by Bennett Gershman, 31 August 2015