“Citizen’s arrest” is a form of arrest that does not involve a police officer. If you are involved in such an arrest, the arrested person, whom you have arrested must be dealt with by the police. You have no right to search or question the arrested person.
As a private citizen, you may arrest and detain a person in any of three situations:
To repeat, it is only if you find a person actually committing a serious crime, you believe on reasonable grounds that such a crime has occurred, or you actually see a police chase in progress.
Extreme care must be taken before making a citizen’s arrest. If you made an error and the arrest is wrongful, you can be sued by the victim. If force was used in the arrest, and if that force is extreme in the circumstances, you may face a criminal charge from the police. In all but extreme cases where there are no other reasonable option, you are better advised to report the matter to a police officer.