Probable Cause vs. Reasonable Suspicion: What’s the Difference?

Probable cause and reasonable suspicion are two similar sounding concepts, but they are applied in very different ways. Both are used by law enforcement officers as a determining factor in whether to detain a suspect for questioning, arrest someone, or search and seize evidence. The U.S. Supreme Court set the standards for reasonable suspicion and probable cause. Although they are similar in some ways, there are key differences between these two concepts.

What Is Reasonable Suspicion?

Probable Cause vs. Reasonable Suspicion: What’s the Difference?In 1968, the U.S. Supreme Court ruled that law enforcement officers are allowed to briefly detain a person if he or she has a reasonable suspicion that that a crime has been committed, the person is engaged in some type of criminal activity, or is planning to commit a crime. This ruling set the parameters for reasonable suspicion. The standard is broader than the standard for probable cause, as it relies heavily on the judgment of law enforcement officers.

Although reasonable suspicion can be subjective, it still must be supported by existing facts and circumstances. For example, if a police officer observes a man walking unsteadily to his car after leaving a restaurant, peeling out of the parking lot, and swerving recklessly into traffic, the officer has reasonable suspicion to pull the man over to check for DUI.

What Is Probable Cause?

The Fourth Amendment to the Constitution guarantees that U.S. citizens have the right to freedom from unreasonable search and seizure, and that a search warrant cannot be issued without probable cause. Although the Fourth Amendment does not provide a definition of probable cause, a 1949 U.S. Supreme Court ruling established that: “Probable cause exists where the facts and circumstances within the officers’ knowledge, and of which they have reasonably trustworthy information, are sufficient in themselves to warrant a belief by a man of reasonable caution that a crime is being committed.”

Police need probable cause to conduct a search of your person or property, arrest you, or issue a warrant for an arrest or a search. In the example above, if the man who is pulled over on suspicion of DUI reeks of alcohol, is slurring his words, and speaking incoherently, the officer has probable cause to arrest him for DUI.

What Are the Key Differences Between Them?

Reasonable suspicion allows a police officer to briefly detain a person who may be in the process of committing a crime, or may have already committed a crime, or may be planning to commit one. However, it does not allow the officer to search that individual’s person, or his vehicle, or his home. To make an arrest or to search and seize evidence, the officer must have probable cause.

In fact, police officers are required to make a sworn statement known as an Affidavit of Probable Cause when they make an arrest. If the facts and evidence fail to support probable cause, criminal charges against the defendant may be reduced or dismissed altogether. A probable cause hearing is held before or after an arrest or search and seizure to determine the legality of probable cause. If the prosecution cannot support probable cause, the case is likely to be dismissed.

If you have been arrested and charged with DUI, call The Bussey Law Firm, P.C. at (719) 475-2555 to get a Colorado Springs DUI attorney on your side. Attorney Timothy Bussey is the only lawyer in Colorado with ACS Forensic Lawyer-Scientist designation. He is also certified on the Intoxilyzer 5000, a certified NHTSA Field Sobriety Test Instructor, and certified in forensic chromatography. His DUI defense case results speak for themselves.