From Criminal Defense Wiki
The Role and Responsibility of a Criminal Defense Lawyer
The criminal justice system is viewed as a three-part system consisting of the judge and jury, the prosecutor, and the defense lawyer. Each part of this system has a specific role. The role of the judge and jury is to render an impartial decision based solely on the facts presented and the laws applicable to the charged offense. In order to decide impartially, the judge and jury must be able to hear arguments from both sides. The prosecutor's role is to argue the side of the state that seeks to prove the defendant's guilt. The defense lawyer's role is to argue on behalf of the defendant. The defendant has no burden of proof. That is, the defendant need not prove his innocence. It is enough simply to point out ways in which the state has not established guilt (e.g., an eyewitness has poor eyesight or an accuser has a motive to lie).