What is the importance of the mirror at the end of the play?

A major dramatic device in Death and the Maiden is Dorfman's use of the mirror in Act 3, Scene 1. At the moment of the play's climax, the stage directions indicate that a giant mirror descends in front of Paulina and Roberto, forcing the audience to study themselves and each other while a spotlight roams around, illuminating various audience members in turn. This highly alienating device entirely takes the viewers out of the "story," encouraging them to instead reflect (literally) on their own feelings about the narrative - their complicity in violations of human rights, their belief in whether or not Paulina's actions are justified, and their own opinions about personal or societal justice.