First, a little history. The concept of citizen’s arrest is usually traced back to medieval Britain, where local sheriffs often relied on (and even encouraged) citizens to help maintain order and apprehend criminals. As the British explored and settled around the world, the citizen’s arrests came in handy in colonies that had little or no formal police forces and were far from the reach of the King’s justice system.
Even after many of Britain’s colonies gained their independence and the wild frontiers became urban centers, DIY policing remained useful. Developing municipal police departments could only handle so many incidents without modern tools like patrol cars and hand-held radio technology. According to Violent Death in the City, a history of crime in 19th century Philadelphia, even with the establishment of the city’s first police detectives in the middle of the century (as late as 1898, there still were only 15 detectives in the police department, and none of them specialized in homicide or much else besides property crimes), private citizens continued to make arrests and even do detective work. Even Herman Webster Mudgett, a.k.a. H.H. Holmes, “perhaps the most celebrated mass murderer of the century,” was caught thanks largely to the work of Frank Geyer, a detective with the private security and detective agency Pinkerton Government Services.
By the end of the 1800s, American cities were becoming large and anonymous enough that everyday people were hesitant to intervene in other people's problems, and were growing dependent on police forces that were more institutionalized and expansive in their powers. Still, the concept of citizen’s arrest stuck around.
Law of the Land
Today, in the United States, private citizens are still able to make arrests under certain conditions. Those conditions differ from state to state, but in many cases, you can make an arrest for 1) a misdemeanor offense committed or attempted in your presence (some jurisdictions specify that the offense has to constitute a “breach of the peace,” the definition for which varies) or 2) a felony offense that has been committed, whether in your presence or not. With a felony committed outside your presence, some jurisdictions specify that the crime must have actually happened, that you knew it happened, and that you have a reasonable suspicion about the identity of the perpetrator before taking action. If you don’t meet those criteria—if you thought a felony was committed and thought you knew who the perpetrator was, but no crime actually occurred, for example—but proceed with the arrest anyway, you open yourself up to a lawsuit in some places.
Again, these rules differ from state to state and even between municipalities in the same state. Your mileage may vary, so check the local laws before you go and get your vigilante on.
Some other things to keep in mind:
- Some jurisdictions require certain procedural steps during a citizen’s arrest—for example, notifying the suspect that they are under arrest and identifying the crime for which they’re being arrested. In other places, you don’t have to notify a person that you’re arresting them if a “reasonable person in the suspect’s position” would know they are under arrest by your actions and the context.
- When it comes to searching someone that you’ve arrested, many states allow you to seize any weapons in their possession and any evidence in plain view, but not conduct a search of their person. Some states grant exceptions for “merchant searches,” where a merchant who arrests a suspect for theft can make a limited search for stolen property in the person’s shopping bags, purse or other packages, but not their clothing.
- Citizen’s arrests usually aren’t subject to the same requirements as an arrest made by a police officer. So, for example, you don’t need to read your arrestee their Miranda rights.
- Using force during an arrest is tricky. Many states allow you to use the “amount of force that is reasonable and necessary” to make an arrest. The definition of “reasonable and necessary” will always depend on the circumstances of the arrest. Some states allow for the use of deadly force if the person making the arrest is faced with the threat of death or serious injury by immediate use of force (that is, someone is about to stab you, not just saying they’ll stab you). In some states, deadly force is also allowed in order to stop a fleeing suspect if reasonable attempts have already been made to restrain them. Crossing the line on the use of force obviously opens you up to serious legal and civil liability.