According to the legend, Emperor Shun's minister Gao Yao had a unicorn goat called the zhi (廌), which he used in criminal proceedings, whenever he was in doubt. The animal instinctively knew the innocent from the guilty; it butted the latter with its horn.
Mentions of the xiezhi in Chinese literature can be traced back to the Han Dynasty, where it is described by the scholar Yang Fu as a "righteous beast, which rams the wrong party when it sees a fight, and bites the wrong party when it hears an argument". It is also described in the Shuowen Jiezi as being "a cattle-like beast with one horn; in ancient times, it settled disputes by ramming the party at fault".
As an inherently just beast, the xiezhi was used as a symbol of justice and law. The Censorate of the Ming and Qing eras, who were responsible for the monitoring of the civil service, wore the xiezhi as a badge of office. Similarly, military policemen of the Republic of China wear badges bearing the xiezhi, and it is engraved on the gavels in the law courts of the People's Republic of China.
In Japan it is known as Kaichi (獬豸), also sometimes referred to as a Shin'yō (神羊 'divine sheep'), and seen as a Chinese equivalent of the Japanese komainu. It is similar to a lion with one horn on the top of its head.
The xiezhi is known as haetae in Korea. According to Korean records, Haetae's body is shaped like a lion and has a horn on its forehead. It has a bell in its neck, and the body is covered with scales. It lives in the frontier areas of Manchuria. 
In ancient Korea, Haetae sculptures were used in architecture during the early Joseon dynasty, as their image was trusted to be able to protect Hanyang (now Seoul) from natural disasters and to give law and order among the populace. Seoul city has officially used Haechi (origin of Haetae) as the symbol of Seoul since 2009.
In English, it is called "the Unicorn-lion" or "an omniscient mythical beast".
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