(2014呼和浩特)
D
The police find most criminals (罪犯) because somebody tells them who the criminals are．They find other criminals by using science and their computers．When there is a bank robbery (抢劫), the police first look through their computers for the names of the bank robbers that they know about．Then they go and talk to any of these robbers who are not in prison (监狱)．They ask them where they were when the robbery happened．If any of these people cannot give a good answer, the police will often use science to find out if one of them is the robber.
Many criminals leave something of themselves at the places of the crimes like a fingerprint or a hair．Or they take something away on their shoes or clothes, like dirt or animal hair．If they leave behind some of their blood or their hair or a piece of skin, it will have their DNA inside it.
