The District Attorney's Office is the public prosecutor.  The district attorney shall attend courts and conduct, on behalf the people, all prosecutions for public offenses.  Cal. Govt. Code §26500

A District Attorney is the representative not of an ordinary party to a controversy, but of a sovereignty whose obligation to govern impartially is as compelling as its obligation to govern at all; and whose interest, therefore, in a criminal prosecution is not that it shall win a case, but that justice be done. As such he is in a peculiar and very definite sense the servant of the law, the twofold aim of which is that guilty shall not escape or innocence suffer.    Burger v. United States 295 U.S. 78, 88

 This obligation is reflected in the office's motto:  Iustitia in Veritate Condita Est

The Foundation of Justice is Truth

The role of the District Attorney's Office is through investigation and trial to obtain justice by doing the best that we can in approaching truth.  That being said, every human system is performed by human beings which means that errors can occur, though we do our best to avoid them.

 The District Attorney's Office has an innocence review process. If new evidence establishes that confidence in a previous conviction needs to be reviewed or questioned we have a procedure in place to address such concerns and make a review.