The Fourth Amendment prohibits unreasonable searches and seizures. This means that government agents have to respect a person’s right to privacy unless they have probable cause to believe the person has committed a crime. With probable cause, officers can search people and places; they can seize any contraband and evidence of criminal activity that they find. Officers can also “seize” people—these seizures are known as arrests.
When is a person under arrest? A person is “seized” for Fourth Amendment purposes whenever someone else in the same situation reasonably wouldn’t feel free to leave. Seizures occur when police officers restrain a person’s movement, either by physical force or by a show of authority.
It’s often very clear that a person is under arrest. For example, an officer yells, “You’re under arrest,” knocks you to the ground, and handcuffs you. In this situation, you are obviously restrained. It’s the same if an officer merely says, “Sit down right here—you’re under arrest,” without using force.
But even if the officer doesn’t formally say that you are under arrest, you might be—or you might be merely detained. If an officer says, “I need to talk to you” and blocks you from leaving, then you are detained. Police are permitted to briefly detain people if they have reasonable suspicion (a standard lower than probable cause) to believe that the detainee has committed or is about to commit a crime. In theory at least, the officer detains the person, asks a few questions, and then either makes an arrest or lets the person go. (To read more about detentions, see When Police May Stop Someone on the Street.)
Sometimes the line between detention and arrest isn’t entirely clear. Generally, if the police keep someone for a long time—say, more than 20 or 30 minutes—or use force or handcuffs, then an arrest has occurred.
Judges have the final word on whether police officers have seized someone. This is often an important question, as it can determine the admissibility of evidence, like statements. For example, police officers need to provide Miranda warnings only if the suspect is under arrest. Also, whether a person was actually arrested can be crucial in police-misconduct litigation.
In deciding whether an officer has arrested a suspect, the court will consider all of the circumstances. Certain facts, such as the following, tend to indicate that an arrest has occurred:
If there isn’t probable cause to support an arrest, then the seizure is invalid, subject to the arrestee challenging it in court. Evidence officers obtain in the course of an illegal arrest is presumptively inadmissible. For more information on inadmissible evidence, see Fruit of the Poisonous Tree.
Police officers can use reasonable force to make an arrest. That means that they can physically restrain arrestees and use greater force against those who resist. What’s reasonable depends on the circumstances.
If you are placed under arrest (whether formally or not), you shouldn’t resist, even if you believe the arrest is unlawful. In most situations, a person has no right to resist even an illegal arrest—doing so can result in criminal charges. (For more information, see Resisting Arrest When Police Use Excessive Force.)
If you have been arrested or otherwise restrained, you should speak with an attorney. Even if the prosecution doesn’t file charges against you, you should know about your options, including potentially getting the arrest purged from your record. (For information, see Expungement and Criminal Records.) An attorney can explain the law in your jurisdiction and, if necessary, provide you with a proper defense.