Probable Cause and Reasonable Suspicion: What Are the Differences?

What Is Probable Cause to Arrest a Person?

Under the Fourth Amendment to the U.S. Constitution, people are protected from unreasonable searches or seizures or the issuance of a search warrant without probable cause. In order to establish probable cause to arrest someone, the police must have sufficient knowledge of facts or evidence that would lead a reasonable person to believe that a crime has been, is, or will be committed and that the person being investigated committed the offense. Arrests made with or without a warrant must be based on probable cause.

A higher standard is required to establish probable cause than reasonable suspicion. It cannot be shown based on an officer’s suspicions or guesses. It must be based on facts and hard evidence. In some cases, sufficient probable cause can develop after the police detain someone based on reasonable suspicion.

There are many ways that the police can establish probable cause to arrest an individual. Examples include smelling alcohol or drugs on them, seeing evidence, such as a gun, drugs, or stolen property, in plain view, or an admission of guilt.

When Is Probable Cause to Search and to Obtain a Search Warrant Established?

To have probable cause to conduct a search, it must be shown that the facts and circumstances established by the police would lead a reasonable person to believe that a crime was committed at the location to be searched or that evidence of a crime exists there. When applying for a search warrant, a police officer must state facts in an affidavit as to why there is sufficient evidence to conduct a search, must specify the place to be searched, and describe the property that will be seized. The judge will make his decision on whether there is sufficient probable cause to issue a search warrant based on the totality of the circumstances.

In some cases, law enforcement is permitted to conduct a search without a warrant if they can establish probable cause. Situations when this may be allowed include:

• When the consent of the person in charge of the property to be searched was obtained
• When the search was conducted in connection with a lawful arrest
• When there was an emergency situation where the public needed protection or evidence would be lost
• When evidence or contraband was in plain view of the police officer