What Is Probable Cause? Legal Definition And Examples

The Fourth Amendment of the U.S. Constitution protects people against being unlawfully searched or unfairly arrested by police. The text of the amendment reads as follows:

“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Because of this amendment, police cannot conduct a search without probable cause of wrongdoing. And they cannot arrest you unless there is probable cause of a crime being committed.

If you are searched without probable cause, any evidence collected must be suppressed. This means it cannot be used against you in court. If you are arrested without probable cause, the arrest is considered invalid and any evidence collected as a result of it will be suppressed.

According to the U.S. Supreme Court, probable cause exists when the “facts and circumstances” that police officers know about, based on “reasonably trustworthy information, are sufficient in themselves to warrant a belief by a man of reasonable caution that a crime is being committed.”

In other words, if a reasonably cautious person was provided with the information the police officers had at the time, that person would have a valid reason to believe that a crime was taking place. This reasonable belief of criminal activity is sufficient to justify either a search or an arrest.

Probable cause is determined based on the totality of the circumstances, so all available information can be considered in deciding if there is valid justification to either conduct a search or to arrest a suspect.

Law enforcement officials must obtain a search warrant before conducting a search when it is possible to do so. A judge should only issue a search warrant if there is probable cause, which means there is enough credible information to suggest evidence of a crime will be discovered during the search.

Law enforcement officials must also obtain an arrest warrant before arresting someone when it is possible and practical to do so. Again, there must be probable cause or credible information suggesting someone most likely committed a criminal offense before an arrest warrant is issued.

Warrantless searches and warrantless arrests can occur in certain circumstances such as when police see evidence of a crime in plain view or when there are exigent circumstances because failure to act could result in the destruction of evidence or harm to others.

When a warrantless search or arrest occurs, law enforcement officials need to provide proof of probable cause after the fact. If law enforcement cannot satisfy the probable cause requirement, the evidence collected will be suppressed or the arrest will be deemed invalid.

Exceptions to the Probable Cause Requirement

There are very limited exceptions when evidence is still admissible even if it was obtained without probable cause.

Exceptions include circumstances where police were acting in good faith, but there was a problem they were unaware of. For example, if police arrest someone because they believe there is a valid warrant, but it turns out a mistake was made and there wasn’t, then evidence collected after the arrest would still be admissible.

There are many different examples of probable cause that could justify a search or justify an arrest. Here are some common examples:

• A law enforcement officer pulls someone over for a traffic violation. The officer notices drug paraphernalia on the front seat or notices the driver is slurring their words and is visibly intoxicated and likely committing a DUI. The drug paraphernalia or the obvious intoxication provides probable cause for a search of the vehicle and/or for an arrest.
• A law enforcement officer observes someone pointing a gun at a convenience store employee in an apparent robbery. This unlawful act the officer observed provides probable cause for arrest.
• A law enforcement officer visits a person’s home after a report of domestic violence and observes weapons in the home and bruises on the alleged victim. This provides probable cause for a search of the home and, if the available evidence creates a reasonable suspicion of a crime, also probable cause for an arrest.

Probable cause may come from officers directly observing evidence suggestive of criminal activity or from credible reports of criminal misconduct from trustworthy sources.

If you believe you were searched or arrested without probable cause, you can argue your constitutional rights were violated.

If a judge determines there was no probable cause and no exceptions such as the good faith exception apply, evidence collected as a result of the unlawful search or unlawful arrest will not be admissible in court against you.

In some cases, you may also have grounds for a lawsuit if you were searched or arrested without probable cause. However, suing the government can be a challenge even in situations where you believe your rights were violated as a result of sovereign immunity rules.

When you suspect a violation of your rights, it is very important to talk with an experienced attorney. If you have been charged with a crime, a lawyer can also help you to determine if you may be able to get evidence suppressed based on a constitutional violation. You should reach out to an attorney ASAP to protect yourself as you navigate the criminal justice system.