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When is an Arrest Legal?

For all practical purposes, the police can arrest a person with or without a warrant, as long as the police believe there is probable cause that he or she has committed a crime. The Fourth Amendment curbs the power of law enforcement by protecting people against unreasonable searches and seizures, and by requiring that probable cause exists before making an arrest. The two major issues courts will look at when determining whether an arrest is legal are whether there was probable cause and whether an arrest was actually made.

Probable Cause

Probable cause exists when police officers have more than a “bare suspicion” that an offense has been committed and that the person they seek to arrest has committed the crime. The police don’t have to be absolutely sure, they just have to honestly believe there is more than a 50 percent chance that the suspect is involved in a crime.


Courts strongly favor arrest warrants as the basis for a proper arrest. Getting a warrant allows for a third-party magistrate to evaluate the facts underlying law enforcement’s contention of probable cause, and an early and objective evaluation of the facts makes it more likely that any evidence obtained during the course of the arrest will be admissible in a future court proceeding.

There are limitations on when the police can make a warrantless arrest, the most notable of which is that police cannot generally enter a suspect’s home without a warrant. Of course there are exceptions; for example, police can enter someone’s home if they believe a violent crime is involved, the suspect is believed to be armed, and there is a likelihood the suspect will escape if not swiftly apprehended.

Was There an Arrest?

Police are free to stop a person on the street and question him or her without the stop rising to the level of an arrest. The difference between a mere “stop” and a full arrest becomes significant in terms of whether or not police can conduct a search, and whether the police must give a suspect Miranda warnings before asking any questions. Courts have defined an arrest as the seizure of a person in which a reasonable person would believe that he or she is not free to leave. In order to briefly detain someone and ask questions, the police must only have a reasonable suspicion that there is some criminal activity afoot and need not meet the higher probable cause standard required for an arrest.

What Happens if an Arrest is Illegal?

Unless there is a civil rights violation — which is rare — the effect of an unlawful arrest mainly impacts what evidence can be presented at trial, as evidence obtained in violation of the Fourth Amendment will likely be inadmissible in any subsequent criminal case flowing from the arrest. No matter how wrong the police were, in most cases of unlawful arrest the only remedy is the exclusion of evidence during a later court proceeding.

Preparing to Meet With a Criminal Defense Attorney

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Preparing to Meet With a Criminal Defense Attorney

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