Fiat justitia ruat caelum was used in the case that was decided in what year?
Fiat justitia ruat caelum:  It was used in the landmark judgment, "Somerset v Stewart", where slavery was held to be unlawful at common law. Somerset v Stewart: Somerset v Stewart (1772) 98 ER 499 (aka "Somersett's case", or in State Trials v.XX "Sommersett v Steuart") is a famous judgment of the English Court of King's Bench in 1772, which held that chattel slavery was unsupported by the common law in England and Wales, although the position elsewhere in the British Empire was left ambiguous.
1772