What Is Probable Cause?

Probable cause is a legal standard that tells the police when they can and cannot arrest someone or search their person, automobile, or dwelling. Probable cause is a limitation on the authority of government agents and is designed to ensure maximum personal freedom for the citizenry, at least to the extent that it is consistent with enforcing the law.

Where Does the Concept of “Probable Cause” Come From?

The concept of probable cause comes from the Fourth Amendment to the US Constitution, applied to the states through the 14th Amendment. You need probable cause to arrest someone, and you need probable cause to search someone and seize their property as evidence of a crime. The general rule is that a warrant is required to stop and arrest or to perform a search and seizure; however, many exceptions to the warrant rule exist.

Definition of Probable Cause

An officer of the law might have probable cause to::

  • Make an arrest if they have access to evidence that would convince a “reasonable person” that a crime is being committed, or is about to be committed, by a particular person; or 
  • Search a location (and seize any evidence found) if they have access to evidence that would convince a “reasonable person” that the location in question holds evidence of a crime.

What would convince this hypothetical “reasonable person,” however? There is no hard and fast rule. The officer needs enough evidence to convince a judge that he was justified in making the arrest or searching the location, despite the subject’s constitutional right to privacy.

The Exclusionary Rule

Under certain circumstances, you don’t need a warrant to make an arrest or conduct a search and seizure. Although the suspect’s lawyer may challenge the officer’s actions later in court, the officer will have the opportunity to prove that their actions were appropriate. 

If the officer’s actions were not appropriate, then nothing that the officer seized (drugs, for example) as a direct or indirect consequence of their inappropriate actions can be used against the suspect in criminal prosecution. This prohibition is known as the “exclusionary rule.”

The Warrant Rule and Its Exceptions

A warrant is a document issued by a magistrate (a type of judge) to justify an arrest, search, or seizure. To obtain a warrant from a magistrate, you must present the magistrate with evidence that amounts to probable cause. 

If the evidence is sufficient, the magistrate will issue you a warrant to make an arrest or conduct a search and seizure. You need a warrant unless circumstances indicate an exception to the warrant rule.

Stop and Frisk

An officer can briefly detain someone and conduct a pat-down of their outer clothing if they have “reasonable suspicion” that the person has committed a crime, is about to commit a crime, or is carrying a weapon. “Reasonable suspicion” is a lower standard that requires less evidence than “probable cause.”

Content, whether expressed verbally or non-verbally, is enough to allow a police officer to conduct a search. Police officers sometimes use tricks to secure “consent.”

Plain View

If a police officer is already located in a place that they have a right to be (not conducting an illegal search, for example), and if the evidence of a crime is in plain view and easy to recognize, the officer may seize it.

Exigent Circumstances

Under certain circumstances, you simply don’t have time to wait for the issuance of a warrant. The suspect might have already flushed their drugs down the toilet by the time you obtain a warrant, for example. Under these circumstances, it may be permissible for the officer to go ahead and act without a warrant.

Hot Pursuit

The “hot pursuit” exception to the warrant rule is similar to the “exigent circumstances” exception. If you are chasing a bank robbery getaway car down the highway, you don’t have time to stop by the magistrate’s office to get a warrant before you pull over the vehicle.

Search Incident to an Arrest

If the officer already has probable cause to arrest you, they can conduct a search of your person incident to the arrest without additional probable cause. 

Automobile Searches

An officer can search a car for illegal items or evidence of a crime if they have probable cause to believe that a search would uncover them. 

In all of the foregoing cases (except stop and frisk and consent), the lack of a need for a warrant doesn’t mean that the officer doesn’t need probable cause. It just means that the officer will need to justify his actions later, rather than justifying them in advance as in a warrant request.

Example of a Search and Seizure Using Several Exceptions to the Warrant Rule

A policeman knocks on the door of a suburban residence. The resident opens the door for the policeman and beckons them in, constituting nonverbal consent. Once the door is open, the officer sees scales and baggies containing white powder, both of which indicate that illegal drugs are being sold. The resident grabs the scales and baggies and rushes into the bathroom closing the door behind him. 

The officer, understanding that the resident intends to flush the drugs down the toilet, kicks down the door and seizes the evidence based on the “exigent circumstances” exception to the warrant rule. It is likely that a court would find that none of the officer’s actions were unconstitutional, despite the lack of a warrant.

Contact a Criminal Defense Lawyer Immediately

If you have been arrested, or if your home or car has been searched and the police have seized evidence against you, you are probably already in trouble. Attempting to defend yourself against criminal charges could result in disaster. Seek an experienced Pennsylvania criminal lawyer to stand and fight for you.