United States Supreme Court Justice White Defined the Role of the Prosecutor
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. The State has the obligation to present the evidence.
United States Supreme Court Justice White Defined the Role of the Criminal Defense Attorney
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. 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.