If the police violate a citizen's constitutional rights, the evidence unlawfully obtained is not admissible in court. Often when a judge suppresses the illegally obtained evidence, the defendant wins the case. Thus because law enforcement officers understand that their misconduct may cause the suspect to go free, they are deterred from violating that suspect's rights. The same is not true for prosecutors. Cases are rarely overturned for prosecutorial misconduct. Most of the time appellate courts will rule that the prosecutor's misconduct was "harmless error." This means that even though the prosecutor violated the rules, it did not make a difference in the outcome of the case. Furthermore, appellate courts rarely name the prosecutor who violated the prosecutor in their written opinions.
While the Hyde Act allows criminal defendants to recover attorney's fees when prosecutors act in bad faith, the prosecutor rarely suffers professional consequences from acting in bad faith. Often a prosecutor acting in bad faith is in violation of the Model Rules of Professional Conduct. Rule 3.8 specifically lists the special responsibilities of the prosecutor and yet prosecutors are seldom disciplined for violating the rules. Even the most egregious ethical violations rarely result in any sanctions.
While most prosecutors seek justice rather than convictions, it is clear that some prosecutors will cheat to win. In the Ted Stevens case, prosecutors intentionally hid evidence that was favorable to the defendant. Under Brady v. Maryland, prosecutors are required to provide a defendant with evidence that may prove his innocence. In Stevens' case, prosecutors didn't just fail to provide the evidence, they hid it. It is hard to believe that a prosecutor would hide evidence that exonerates a defendant, but it happens.
There have been cases where the prosecutor knew neither the blood type nor DNA on key pieces of evidence matched the defendant in a murder case and chose not to disclose that fact or produce the evidence. In other cases, prosecutors failed to disclose plea agreements with snitches or payment for witness testimony.The reason why the prosecutorial misconduct occurs is unclear. In some instances it appears to be politically motivated. In other instances it appears the prosecutor wants justice for the victim so bad that he subverts justice in order to please the victims. While prosecuting crime is a noble cause, the end never justifies the means. While mistakes are understandable, intentionally hiding evidence or lying to convict an innocent person is inexcusable. In order for justice to exist, prosecutors must follow the rules. Criminal defense attorneys are charged with holding prosecutors accountable and bringing the misconduct to the attention of the court and sometimes the public.