1. An instigator or setter on, one who promotes or procures a crime to be committed. Treason is the only crime in which every one concerned is a principal. [Whart.] 2. In KJ (Sri Lanka) v. Secretary State for the Home Department, [2009] Imm AR 674 "IT follows that mere membership of an organisation that, among other hand, a person who knowingly participates in the planning or financing of a specified crime or act or is otherwise a party to it, as a conspirator or an aider or abettor, is as much guilty of that crime or act as the person who carries out the final deed.". Regina (JSC Sri Lanka) v. Secretary of State for the Home Depet ., [2011] 1 A.C. 184.