Each jurisdiction has its own legal requirements for a valid citizen's arrest, but most generally require you to first announce that you are making a citizen's arrest, detain or restrain the suspect with a reasonable amount of force, and then hand the suspect over the the police. There are many legal factors surrounding any action on the part of an ordinary person making an arrest. The potential pitfalls are so severe that unless you have made a study of the specific citizen's arrest law in your jurisdiction, you should likely leave suspects to be handled by the police except under extraordinary circumstances.
A citizen's arrest is any restraint or detention of a criminal suspect by a person who is not an authorized law enforcement official. Any person, regardless of nationality, can make an arrest under this type of law in the right circumstances. Most jurisdictions with common law legal systems allow ordinary people to make arrests, and the broad outline of the actual procedure is basically the same. There are distinct differences in the underlying legal standards that determine if the arresting citizen had the right to avail himself of this authority in the first place and whether the authority was exercised with requisite care.
To make a citizen's arrest, you must first witness a crime. Some jurisdictions require you to see the crime happen yourself. Others allow you to apprehend a suspect if he is fleeing from an area and you have a reasonable suspicion that he has just committed a crime. Most jurisdictions require the crime to be a felony, but some allow arrest in the case of certain types of misdemeanors. The arrest must always be necessary to prevent some further injustice, otherwise a witness is required to call and wait for police.
You must restrain or detain a person to make a citizen's arrest using only the amount of force necessary to control the situation. This is a subjective legal standard that courts qualify as reasonable force, or the amount of force a reasonable person would have used in similar circumstances. Any legitimacy of a use of force on another person is subject to the prerequisite legal standard that there were reasonable grounds to suspect a person's guilt.
All jurisdictions require you to turn over the arrested suspect to law enforcement at the earliest opportunity. Making a citizen's arrest is not something to be undertaken lightly unless you have a thorough understanding of the applicable law. Incorrectly applying the law can expose you to civil and criminal liability for assault, battery, wrongful arrest, false imprisonment, kidnapping, discrimination, bias crimes, or other illegal acts.
