How to Make a Citizen's Arrest
If you're unsure about when you can make a citizen's arrest, check the laws in your local area, because the definition of a citizen's arrest and when you can make one varies from state to state. Detain someone if you witness them committing a felony, like murder, theft of more than $500 worth of property, rape, or a hit-and-run. Before you attempt the arrest, make sure you're aware of your physical abilities and that you can actually detain the person, since your intervention may escalate the situation and make things worse if you can't. When you detain them, tell them you're making a citizen's arrest. Then, use reasonable force to detain them until law enforcement arrives.
Witness a crime taking place. It's not a good idea to make a citizen's arrest unless you've actually seen a crime happening. When the police arrive, you will have to provide "probable cause" for making the arrest. This means you'll have to show that you had a reasonable belief that the person you arrested committed a crime. For example, if you see a person use a knife to stab another person, you've seen a crime and can detain the perpetrator. Determine whether the crime is a felony. In most states, it's legal to make a citizen's arrest when you see or have reasonable cause to believe that a person committed a felony, even if the felony was not committed in your presence. Citizen's arrests are not usually legal when the crime committed is only a misdemeanor. Since the definition of a felony varies slightly from state to state, it's a good idea to read up on your state's individual laws. The following is a list of crimes that are typically a felony : Murder, rape, or assault resulting in bodily injury Theft of more than $500 worth of property Indecent exposure before a child Hit and run Arson Find out the law in your location. In some other states, you must always see the offense take place regardless of whether the offense is a felony or misdemeanor breach of the peace. In these states the citizen's arrest statute does not allow a citizen's arrest based upon "probable cause". Decide if the crime was a "breach of peace. " In some cases, you may make a citizen's arrest for misdemeanors if the misdemeanor can also be considered a breach of peace. Misdemeanors that are considered breaches of peace in some states include public brawling or public intoxication. If you arrest someone for committing a crime that falls into this category, you must have seen the crime firsthand. Decide if you can safely make a citizen's arrest. Be sure you can physically restrain the person you want to arrest before you try to. Misunderstanding your physical capabilities may put you or others in harm's way. If you make a citizen's arrest, the situation could easily escalate beyond your control. Remember to think hard before making a citizen's arrest, especially if the perpetrator is armed. Be prepared to accept the consequences. Be sure you fully understand the circumstances in which you can make a citizen's arrest. You may want to research the rules specific to your state. If so, contact a lawyer through your State Bar Association or local law enforcement office. If it turns out you didn't have grounds to make the arrest, you could be sued for false imprisonment, assault and battery and other torts. You may also face criminal charges. Don't make a citizen's arrest unless you're willing to face these risks. Tell the person you're making a citizen's arrest. There are no specific words you must say, but you must make it completely clear that you are making a citizen's arrest. The person you're arresting must fully understand what's happening. Explain to the potential criminal why you are making a citizen's arrest. If you cannot provide him or her with this information, then you shouldn't be making the arrest. In some states you must communicate to the individual the specific criminal offense for which the individual is being arrested for. Leave it to the police to read the person his or her rights. For now, you only need to say that you're making an arrest. Detain the person using reasonable force. You can only use the amount of force required to detain the person until the police arrive. Using a greater amount of force exposes you to legal trouble. Be careful not to harm the perpetrator unless it's absolutely necessary. Call and deliver the suspect to law enforcement. Call law enforcement right after the person is detained. Some statutes in states like California and Minnesota require that a person take the arrested individual before a judge or peace officer “without unnecessary delay.” But, if you try to transport a suspect on your own and you conducted an improper citizen's arrest, you may be subjected to a lawsuit for false imprisonment. Ask someone to stay with you. If you can't deliver the suspect or your state doesn't need you to, ask a third party to stay with you. Wait for law enforcement to arrive. If possible, avoid watching the person you've arrested alone. Having a third party help you detain the person is best for everyone's safety. The third party may be helpful in making sure the encounter doesn't get violent and might be able to serve as a witness. Explain in full detail what you saw. When law enforcement arrives, explain what you saw in full detail. Law enforcement will probably ask you to give a statement. Make sure to include everything that you saw. Explain your actions during the criminal act and the citizen's arrest. Be clear about any force you had to use to arrest the suspect. Depending on your state, transporting an individual away from the scene of the crime may constitute kidnapping or criminal confinement, regardless of whether you have lawful grounds for citizen's arrest. Don't make an arrest if you didn't see the crime. While you may think you have all the evidence you need to believe someone has committed a crime, your understanding of the events may be wrong. Don't make a citizen's arrest if you overhear someone talking about robbing a bank. If you're wrong, you may be at fault. Call the police instead. Always remember, an improper citizen's arrest can result in prosecution for crimes like kidnapping. For example, just because you see a crowd of people chasing a suspect or a victim asking for help, doesn't necessarily mean you have grounds to arrest someone. Don't arrest someone you believe is about to commit a crime. The crime must have already happened in order for you to legally make an arrest. Don't arrest someone if the crime hasn't yet been committed. Call the police instead. Don't use excessive force. Even the police are not allowed to use excessive force when taking a suspect into custody, so you, as a private citizen, should be especially careful about this. Otherwise, you may be charged with battery, even if the suspect you apprehend is guilty of a crime. The use of deadly force is usually not allowed unless the perpetrator is attacking you or someone else. Don't use a weapon against the perpetrator when you can use your own strength. For example, you can tackle someone to the ground rather than hitting him or her. Don't make a citizen's arrest if you could easily call the police instead. As a private citizen, it's not your job to make arrests. If it is at all possible, you should always leave policing to those who have a legal authority to do so--the police. Otherwise, your actions might put you, the alleged perpetrator and the general public, at risk. Your actions may also be viewed as vigilantism, which is not legally protected action if you step beyond the authority explicitly granted to citizens by the law. Keep the detained suspect safe. Once you have detained someone, you are responsible for what happens to the person while he or she is under your control. Make sure they are not in the road, where they could be hit by a car, and make sure they are protected from onlookers who might try to attack them. 
Witness a crime taking place. Determine whether the crime is a felony. Find out the law in your location. Decide if the crime was a "breach of peace. Decide if you can safely make a citizen's arrest. Be prepared to accept the consequences. Tell the person you're making a citizen's arrest. Detain the person using reasonable force. Call and deliver the suspect to law enforcement. Ask someone to stay with you. Explain in full detail what you saw. Don't make an arrest if you didn't see the crime. Don't arrest someone you believe is about to commit a crime. Don't use excessive force. Don't make a citizen's arrest if you could easily call the police instead. Keep the detained suspect safe. 