Real policemen hardly recognize any resemblance between their lives and what they see on TV. There are similarities, of course, but the cops don't think much of them. The first difference is that a policeman's real life revolves round the law. Most of his training is in criminal law, and what is more, he has to apply it oh his feet, in the dark and rain, running down an alley after someone he wants to talk to. Little of his time is spent in chatting to a scantily-clad lady or in dramatic confrontation with desperate criminals 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--or not--of stupid, petty crimes. Most television crime drama is about finding the criminals 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 cases like murders and terrorist attacks where failure to produce results reflects on the standing of the police. The police have elaborate machinery, which eventually shows up most wanted men. 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 different evidence. Much of this has to be given by people who don't want to get involved in a court case. So, as well as being overworked, a detective has to be out at all hours of the day and night interviewing his witnesses and persuading them, usually against their own best interests, to help him. A third big difference between the drama detective and the real one is the unpleasant moral twilight in which the real one lives. Detectives are subject to two opposing pressures first, as members of a police force they always have to get results. Second, they have to observe the rules. They can hardly ever do both. Most of the time some of them have to break the rules in small ways. It is essential for a policeman to be trained in criminal law ______.