The world of law as practiced in the real world is far removed from that usually discussed by law professors and philosophers or shown on television and in movies. In idealized or fictional cases the law always operates formally and may seem to pursue some abstract quest for justice. In the everyday practice of law, however, things work differently--it is all about cobbling together the most compelling and convincing story possible either for or against a defendant. Attorneys will shoehorn into their arguments any information they can find that might further their ends. The legal system therefore efficiently uses every scrap of relevant data that might pertain to a case--including findings such as brain scans that might not normally be formally admissible during trials.

The reality is that few criminal cases--only about 3 percent of federal ones and a bit more than 4 percent at the state level--ever go to trial. Normally, after someone is charged with a crime, the prosecution and the defense attorneys engage in confidential plea bargaining away from the courtroom. The plea negotiations are usually conducted informally (although in intense cases, such as those that might involve the death penalty, they can take on the appearance of a condensed sentencing hearing).