Here is an interesting post from the Australian Professional Liability Blog on prosecutorial obligations. Although the language used is different in many ways, the underlying duties discussed are very similar to those in the rules of conduct in most states, the ABA Model Rules and the Restatement. I did find interesting that more than one source mentions that prosecutors have a duty to help the court "arrive at the truth," something I would not say since due process, rather that "the truth" seems to be the main goal in our system. As a famous movie quote goes, "the truth is we don't know what the truth is." (The first person who can name the movie gets a prize.)
Rather than mention a duty to help find the truth, the text of the comment to ABA Model Rule 3.8 states: "A prosecutor has the responsibility of a minister of justice and not simply that of an advocate. This responsibility carries with it specific obligations to see that the defendant is accorded procedural justice, that guilt is decided upon the basis of sufficient evidence, and that special precautions are taken to prevent and to rectify the conviction of innocent persons.. . . "