A District Attorney is?

brings criminals to justice

A District Attorney is the Chief Prosecutor for the local province, which is demarcated by the government for their administrative purpose.

Explanation:

To further initiate a criminal proceeding for those law-breaking anti-social groups or an individual's the district attorney and assistant district attorneys are responsible. They are the ones responsible for presenting the case on behalf of the government.

Their responsibilities are in collusion with the law enforcement agency and they will analyze the case and determine whether the case is fit for trial. And their responsibility includes managing the office of the prosecutors. They will act as a facilitator between the cases in trial court and law enforcement officer.