Real Policemen and Policemen on TV
Real policemen hardly recognize any resemblance between their lives and what they see on TV—if they ever get home in time. There are similarities, of course, but the policemen don't think much of them.
The first difference lies in that a policeman's real life centers around the law. Most of his training is in 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 narrow street after someone he wants to talk to.
Little of his time is spent in chatting to pretty girls or in dramatic confrontations（对峙）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, minor 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 cases like murders and terrorist attacks—where failure to produce results reflects on the standing of the police—little effort is spent on searching.
Having made an arrest, a detective（侦探）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. 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 interests, to help him.
15.What is the main idea of the passage?