Under what condition can a private actor arrest for a misdemeanor?

A private actor may arrest for a misdemeanor when the misdemeanor is committed in their presence. This principle is grounded in the common law doctrine that allows an individual to take action against a wrongdoer when they directly observe the offense occurring. The rationale behind this is that a private citizen is deemed to have firsthand knowledge of the crime, thereby justifying their intervention to maintain public order.

When someone witnesses a misdemeanor, such as shoplifting or vandalism, they have the capacity to act because they can verify the crime took place. This capability might also help in preventing any further harm or preserving evidence related to the crime. It's important to note that the scope of this authority typically extends only to misdemeanors and not to felonies, unless in exigent circumstances where immediate action is warranted.

The notion of an arrest on private property or informed about a crime by someone else does not fulfill the legal requirement that the private actor must directly observe the offense. Additionally, the refusal of police to act does not provide a legal basis for a private individual to intervene; their authority to arrest must be based on their own observation of the misdemeanor.