Law enforcement officers have the obligation to convict the guilty and to make sure they do not convict the innocent. They must be dedicated to making the criminal trial a procedure for the ascertainment of the true facts surrounding the commission of the crime. To this extent, our so-called adversary system is not adversary at all; nor should it be. But defense counsel has no comparable obligation to ascertain or present the truth. Our system assigns him a different mission. He must be and is interested in preventing the conviction of the innocent, but, absent a voluntary plea of guilty, we also insist that he defend his client whether he is innocent or guilty. The State has the obligation to present the evidence. Defense counsel need present nothing, even if he knows what the truth is. He need not furnish any witnesses to the police, or reveal any confidences of his client, or furnish any other information to help the prosecution’s case. If he can confuse a witness, even a truthful one, or make him appear at a disadvantage, unsure or indecisive, that will be his normal course. Our interest in not convicting the innocent permits counsel to put the State to its proof, to put the State’s case in the worst possible light, regardless of what he thinks or knows to be the truth. Undoubtedly there are some limits which defense counsel must observe but more often than not, defense counsel will cross-examine a prosecution witness, and impeach him if he can, even if he thinks the witness is telling the truth, just as he will attempt to destroy a witness who he thinks is lying. In this respect, as part of our modified adversary system and as part of the duty imposed on the most honorable defense counsel, we countenance or require conduct which in many instances has little, if any, relation to the search for truth.
— Mr. Justice White’s dissenting opinion in United States v. Wade, 388 U.S. 218, 256-58 (1967) (Emphasis added.)
Prosecutors may read this famous opinion differently, but I read it to say that the mission of defense counsel is to do justice.
Justice is the absence of crime. Convicting the innocent is a crime if ever there was one. The “justice” of prosecutors is justice only in a derivative sense. It’s the use of punishment — which itself outwardly resembles crime — to try to prevent or deter future crimes and/or somehow negate or provide satisfaction for crimes which have already occurred. Its purpose is to approximate so far as possible justice in its root sense, but historically hasn’t gotten us very far.