I think that Hale probably is one of the best representations of why justice did not prevail in Salem. Hale's disposition as one that would be willing to do just about anything in the name of absolute certainty is a reflection of the Puritanical failings that Miller seeks to bring out in the drama. Hale's notion of certainty and absolutism are what bring him to Salem and end up being manipulated by the people of Salem. It is this guilt that ends up haunting him at the end of Act III. Yet, Hale is still convinced in his authenticity in trying to get those who have been falsely imprisoned to "confess" to something they did not do in order for them to live. It is here where the failures of Salem and the lack of justice in Salem are the most evident. Miller constructs Hale as one where there will always be a sense of justice being absent. Hale's belief in the sanctity of life is one that almost degrades it. Hale wishes to force confessions out of those imprisoned so that they may live. Yet, in doing so, they must lie. It is here where justice does not prevail, as another lie must be assigned in order for those who have been imprisoned because of lies to live.
Hale's characterization in this light demonstrates how justice does not prevail in Salem. His recognition of his own sin and his own wrong gives hope. Yet, his belief that offering up a "simple" lie in order to save oneself is acceptable is simply a variation on the lack of justice that has gripped Salem and caused its demise. Miller makes it clear that Hale's character, albeit an admirable one, is flawed in his embrace of lies to any end, as they can be easily manipulated by those in the position of power.