If Congress declares a person to be guilty of a crime without having been given a trial, this would be an example of a Bill of Attainder. A Bill of Attainder is defined as the legislative act of convicting a person to punishment, without a previous trial. The Constitution of the United States, in its Article 1, states that "no Bill of Attainder or ex post facto law will be passed". The constitution's statement tries to represent the idea that courts exist in order to judge a case and as a consequence of such action, impose or not a punishment.
