Real Policemen hardly recognize any resemblance between their lives and what they see on TV. The first difference is that a policeman's real life revolves around criminal law. He has to know exactly what actions are crimes and what evidence can be used to prove them in court. He has to know nearly as much law as a professional lawyer, and what is more, he has to apply it on his feet, in the dark and rain, running down a street after someone he wants to talk to. Little of his time is spent in chatting, he will spend most of his working life typing millions of words on thousands of forms about hundreds of sad, unimportant people who are guilty of stupid, petty crimes. Most television crime drama is about finding the criminal: as soon as he's arrested, the story is over. In real life, finding criminals is seldom much of a problem. Except in very serious eases like murders and terrorist attacks little effort is spent on searching. Having made an arrest, a detective really starts to work. He has to prove his case in court and to do that he often has to gather a lot of evidence. The third big difference between the drama detective and the real one is the unpleasant pressures: first, as members of a police force they always have to behave absolutely in accordance with the law secondly, as expensive public servants they have to get results. They can hardly ever do both. Most of the time some of them have to break the rules in small ways. If the detective has to deceive the world, the world often deceives him. Hardly anyone he meets tells him the truth. And this separation the detective feels between himself and the rest of the world is deepened by the simplemindedness—as he sees it—of citizens, social workers, doctors, law-makers, and judges, who, instead of eliminating crime punish the criminals less severely in the hope that this will make them reform. The result, detectives feel, is that nine-tenths of their work is recatching people who should have stayed behind bars. This makes them rather cynical. A policeman has to be trained in criminal law because ______.