That is a misunderstanding of what "faith alone" means. I mean, it depends what is the object of your faith. To use your analogy, the criminal would not use "belief in the judge's authority" as a defense, but rather belief that somebody else had paid the penalty for his crimes.
After I privately and politely informed her that she had committed a grievous sin (like we are called to do – see Matthew 18:15-17, Galatians 6:1, and Ephesians 4:15), she immediately jumped to the “Who are you to judge?” defense and paired it with the “Jesus paid the price” line.
Read 1 Cor. 3:12-15 --> "Now if anyone builds on this foundation with gold, silver, precious stones, wood, hay, straw, each one’s work will become clear; for the Day will declare it, because it will be revealed by fire; and the fire will test each one’s work, of what sort it is. If anyone’s work which he has built on it endures, he will receive a reward. If anyone’s work is burned, he will suffer loss; but he himself will be saved, yet so as through fire." To me, this passage is telling me that all my actions will be judged and that, depending on how they are judged, I will earn or lose rewards. But my salvation was assured the moment I placed my faith in Jesus and what He did at the cross. If I don't do any works that will survive the fire (judgment) Paul says that I "will suffer loss (of rewards) but I will be saved yet so as through fire".
God's mercy is subject to a paradox much like earthly charity: if someone who attempts to live prudently and make preparation for things that might go wrong, gets caught by misfortune beyond what he could reasonably have anticipated, the granting of assistance to such a person may benefit both the giver and recipient. On the other hand, an expectation that relief will be available in case of calamity, thus obviating any need to prepare oneself, is highly toxic. The ideal behavior for an earthly charity would often be to prioritize relief based upon the extent to which people strive to avoid needing it. Earthly charities often find it hard to measure such things, but God will not. Those who seek to avoid needing his forgiveness while recognizing that their efforts may be insufficient, will receive it; those who expect to rely upon it his forgiveness unless or until they realize such reliance as being a major sin in and of itself.