Repentance prior to a court conviction

It is narrated: >The Prophet (peace and blessings of Allaah be upon him) said: “The one who repents from sin is like one who never sinned.” And the one who did not sin cannot be punished. Does this mean that if someone is found guilty of murder or rape, but he repents prior to the trial, he can be let off without any form of discretionary punishment? What if it so happens that the forgiveness prior to the trial was completely insincere or worse yet, there is a great chance that person may commit the crime again?