Section 141 of the Indian Penal Code (IPC) defines the unlawful assembly. An assembly of five or more persons is designated an “unlawful assembly” if the common object of the persons composing that assembly is to commit any of the activities mentioned in section 141.
Purpose of assembly is the crucial fact which converts a lawful assembly into an unlawful assembly. Unlawful means not conforming to, permitted by, or recognised by law or rules. Assembly means a group of people gathered together in one place for a common purpose. Section 141 and 149 create a specific offence co-jointly with the common object and unlawful assembly.
Section 149 creates a specific and distinct offence. It imposes constructive or vicarious criminal liability of the members of the unlawful assembly for the wrongful acts committed under the common object by any other member of the assembly. If an offence is committed by any member of such unlawful assembly in the pursuance of the shared object, all the members shall be liable for that offence.
Presence of a person in that assembly is the most vital fact to decide his liability for the commencement of that offence. In Baladin v. State of Uttar Pradesh, AIR1956 SC 181, the supreme court expressed that mere presence in an assembly does not make a person, who is present, a member of an unlawful assembly. If it is shown that he had done something or omitted to do something which would make him a member of an unlawful assembly, or unless the case falls under Section 142 IPC.
It must be proved that he was one of the persons constituting the assembly and he entertained long with (other members of the assembly) the common object as defined by Section 141 IPC.
Some overt act is necessary to implicate a person for the offence committed by the unlawful assembly. In Masalti v. State of U.P., AIR 1965 SC 202; the supreme court held that it must be shown that he had committed some overt illegal act or had been guilty of some unlawful omission in pursuance of the common object of the assembly. The same principle is reiterated by the supreme court in Om Prakash Vs. The state of Haryana, (2014) 5 SCC 753.