Todays policemen in large cities throughout the world rely on modern inventions to help them in their work. In most places motor scooters and police patrol cars have done away with the need to patrol on foot or on horseback. Policemen use telephones, conveniently located throughout their districts, to make immediate contact with headquarters. Radio, television, and computers help to speed the work of the modern force. Even boats and helicopters are part of the equipment of metropolitan police departments. New technical inventions are widely used to fight crime and speed the solution criminal cases. Electronic computers reduce from hours to minutes the time spent in searching for fingerprints. Witnesss descriptions of a criminal are coded and fed into a computer. The machine then sorts through the picture file of known criminals and selects the name and photograph of the most likely suspect. Lie detectors are used to uncover the truth.