The essence of the offence under Section 143 is the combination of several persons, united in the purpose of committing a criminal offence, and that consensus of purpose is itself an offence distinct from the criminal offence which these persons agree and intend to commit. An assembly lawful in itself does not become unlawful merely by reason of its lawful acts exciting others to do unlawful acts.
It is true that common object has to be a matter of inference, but for establishing that an unlawful assembly had been formed, the prosecution has to show not merely that it was likely that the assembly in question has for its object one or more of the things specified in Section 141 but that the existence of such object is the only reasonable conclusion possible in the circumstances of the case. In Masalti v. State of U.P., it has been held to the effect that till it is established that the accused were not present at the alleged scene of offence only as spectators, they cannot be convicted for offences under Sections 143 and 149, I.
P.C. It is the duty of the prosecution to establish that the accused had acted in persecution of the common object of the assembly. Till that fact is proved, the accused cannot be convicted. Proof: For an offence under Section 143, the prosecution has to prove— (1) That the assembly in question consisted of five or more persons; (2) That the object of the persons so assembled was any one of those objects specified in Section 141; (3) That the said object was common to the persons assembled; (4) That the accused joined, or continued in such assembly; (5) That he did so intentionally; and (6) That the accused did so after being aware of the facts specified in Section 141.