The Amazing Inebriomatic could tell if a person was drunk just by breathing into the device. The idea of using breath to detect traces of alcohol was described as early as 1874, but it wasn't applied to a practical use until 1927. The first device of this kind used by police officers was the drunkometer, which began to be used in roadside stops in 1931. Beginning in 1954, the device began to be commonly known as a breathalyzer or breathalyser.
In 1931 at the Hill Valley Science Exposition, Officer Danny Parker told Marty McFly that the device would help law enforcement as it could be used to tell whether someone was drunk just by breathing into it. He asked Marty if he wanted to try it, but Marty declined.