The Five Knights' case (1627) 3 How St Tr 1 (also Darnel's or Darnell's case) (K.B. 1627), is an English habeas corpus case of major significance in the history of English and later United Kingdom constitutional law.
The case was brought in 1627 by five knights who were being held in detention by King Charles I. Charles had imposed forced loans, and when the knights argued that such loans were illegal and refused to pay, they were imprisoned without trial. The prisoners sought habeas corpus and an order from a common law court that the king should specify what law they were alleged to have broken. The king refused, simply stating that they were being held per special mandatum domino regis (by special command of the lord the king). The court declined to release the prisoners, holding that under the common law the king was not required to be more specific.
Parliament rapidly passed legislation to overturn the result, in the Petition of Right 1628, marking the first of a series of legislative changes and court cases that ultimately led to the modern constitutional understanding of habeas corpus as a protected guarantee of fundamental liberty, in the Habeas Corpus Act 1679.