The Polygraph is an important tool used for police interrogation. There are many details and questions about the polygraph. Examples of these questions and details are what is a polygraph?, is there any history behind this machine?, and Why is it important? Invented in 1921 by medical student James Mikenzie, the polygraph or lie detector would soon become an important tool used in modern police interrogation. The polygraph works by strapping signals to the suspect. These signals are strapped onto places like the chest and arms. They are strapped to the chest to monitor blood pressure and pulses. They are strapped to the arms to monitor things like skin reactions. After the suspect is strapped in and the signals are attached to a machine the interrogator asks a series of ten questions. Examples of these questions includes are the lights on?, What day is it? And what’s your name? If the blood pressure rises in the interrogation this could mean that the subject is lying. The polygraph did not become the way it is overnight. It took many years to perfect the polygraph. The earliest example of the polygraph comes from ancient China. This polygraph worked by having the suspect having the suspect hold rice in there mouth. If the rice was dry at the end of the innate rotation this meant they were lying. The earliest version of the modern lie detector was made in 1921 by John Larson. This machine measured blood pressure. Soon after in 1924 police first started using this machine in interrogation. Later the polygraph was equipped with a motorized pen to make recording the results later. Years later the machine also recorded skin. In 1992 the polygraph was perfected by making the recordings of bloodpressure, and skin computerized. The reason for the results being computerized was because people believed it would be more efficient. Today many government agencies use the polygraph including the most important agiencies such as the FBI. However critics have argued that the some people do not know what to do in a polygraph test and can react in different ways. In conclusion the polygraph has changed over many decades to become the important police tool it is today.