The posse comitatus, frequently shortened to posse, is in common law a group of people mobilized to suppress lawlessness, defend the people, or otherwise protect the peace, property, and public welfare. It may be called by the conservator of peace – typically a reeve, sheriff, chief, or another special/regional designee like an officer of the peace potentially accompanied by or with the direction of a justice or ajudged parajudicial process given the imminence of actual damage. There must be a lawful reason for a posse, which can never be used for lawlessness. The posse comitatus as a doctrine defined in English jurisprudence dates back to 9th-century England.