The American legal system places certain responsibilities onto police officers. The most important of those responsibilities have to do with when it is appropriate to stop or arrest a person. Because being stopped by police is a major deprivation of liberty and constitutes its own form of harm, the legal system wants to restrict those encounters to only those times that an officer has reason to suspect that something is amiss. With this in mind, all people should be acquainted with the terms probable cause and reasonable suspicion. Though these two are often used in concert, they are distinct. It is in their differences that some of the most important principles of police stops are found.
In order to conduct a stop under the so-called Terry doctrine, an officer must have reasonable suspicion that criminal activity either has happened in the past or will be happening some time in the future. Reasonable suspicion, being a somewhat broad concept, is all about the facts that an officer can articulate to justify the belief that a crime is afoot. It is based in part on the training and professional experience of the officer. Likewise, it deals with the totality of the circumstances. When determining whether reasonable suspicion exists, one must ask whether, given all of the facts as they are known to an officer, it was reasonable to presume that a crime might have been happening.
The higher standard of probable cause
Probable cause is undoubtedly a higher standard than reasonable suspicion. Probable cause is the sense that with all of the concrete facts that are known at the time of the determination, it is more likely than not that a crime took place. The word probable is key there, as there must be a greater than 50% probability that a crime happened. Probable cause is used in two ways. First, it is used in order to proceed with a criminal case. A court will look at the evidence against a person and determine whether there is probable cause to proceed with the case. Probable cause is also used by officers to make arrests and seek out warrants.
Reasonable suspicion and probable cause are both doctrines used by police officers and courts to ensure that when a person is stopped or arrested, it is for good reason. Reasonable suspicion must be more than just a mere hunch on the part of the office, and probable cause goes up to a standard even above that. If reasonable suspicion does not exist to think that a person is involved in criminal activity, then officers have no right to stop and detain citizens. Likewise, without probable cause, the criminal justice system cannot move forward.