Ray - In part the problem is that too many of our prosecutors share the common misunderstanding that their job is to win and to defend convictions at all costs.

Our criminal justice system is not supposed to be purely adversarial.  Prosecutors represent the State.  Their "client" wins when the outcome is correct.  i.e. They (and their supervisors) should regard an innocent person being acquitted as "win" and not just those cases in which the guilty were convicted.

Unfortunately, not every prosecutor sees the world this way and those that do often report to people who don't.