Reasonable Suspicion

The term reasonable suspicion refers to a standard by which police officers are judged to have authority to briefly detain a person. Reasonable suspicion is a less strict standard then probable cause, but has very limited applications. To explore this concept, consider the following reasonable suspicion definition.

Definition of Reasonable Suspicion


  1. A legal standard giving law enforcement the right to briefly detain someone, and to search their person for weapons.


1968    U.S. Supreme Court ruling on police officers’ right to frisk detainees

What is Reasonable Suspicion

Reasonable suspicion is a legal term that refers to a police officer’s reasonably justifiable suspicion that a person has recently committed a crime, is in the process of committing a crime, or is soon going to commit a crime. This gives the officer the right to temporarily detain that person, and to do a pat-down search of his clothing to ensure he has no weapons.

Reasonable suspicion, as a standard of belief or proof, is less stringent that probable cause, and is intended to enable law enforcement officials to do their jobs in enforcing the law, preventing crime, and to help keep them safe during their interactions with potential suspects.

Reasonable suspicion, however, is more than just a hunch. A police officer who has detained a person must be able to describe a specific set of circumstances or facts that would lead any objectively reasonable law enforcement officer to suspect the individual is, or has been, engaged in a criminal activity.

Stop and Frisk Based on Reasonable Suspicion

Americans are protected against unreasonable searches and seizures by the Fourth Amendment to the U.S. Constitution. Similarly, people have a right to not be arrested or held by law enforcement without due process. However, law enforcement would be a pale imitation of justice if their hands were tied, being unable to stop people they reasonably suspect of criminal activity, in order to investigate further.

This is the reason for the reasonable suspicion standard, which allows officers to stop or detain people temporarily. Enabling police officers to do this, without allowing them to be reasonably sure the person does not have a weapon on them, exposes the officers to unreasonable danger.

In recent years, there has been some controversy over some jurisdictions’ policies to “stop and frisk” people for no clear reason. Such policies have fallen, in many cases, to cries of racial profiling, and other complaints of civil rights violations.

Indeed, in order for police to lawfully pull someone over in their vehicle, or to stop them in the course of their day, they must have some reasonable suspicion that the person is engaged in unlawful activity. When police do stop someone with reasonable suspicion, they are allowed to frisk him, or do a pat-down search of his clothing, for weapons.

They are not allowed, in such a circumstance, to search the individual’s person for other items, such as drugs. In order to legally search for drugs or other items, law enforcement officers must have probable cause. It is true, however, that if the officer finds something illegal – such as drugs – during the allowable pat-down, it can be seized, and may provide probable cause for further search.

For example:

Steven was driving away from a neighborhood known for its drug activity, when police stop him. The officer advises him that his car’s registration is expired, and asks for Steven’s driver’s license, registration papers, and proof of insurance. When the officer runs a driver’s license check, he discovers that Steven has a warrant for failing to appear in court when ordered.

The officer had reasonable suspicion that Steven was acting illegally by driving a vehicle that was not properly registered, when he stopped him. Taking Steven into custody for the warrant, the officer searches Steven’s clothing for weapons, and discovers several small baggies of white pills stuffed in the lining of his jacket’s pocket.

Although the officer had no probable cause to search Steven’s car, or to engage in a very thorough search of his person initially, he did have the right to search for weapons. The drugs that were discovered during this permissible search can then be used to charge Steven with another drug-related crime.

Reasonable Suspicion vs. Probable Cause

Both reasonable suspicion and probable cause have to do with determining when police officers can stop or detain a person, search for evidence, and arrest a person.

Probable cause means that a police officer must have knowledge of enough facts and circumstances to believe evidence of a specific crime at the location to be searched. This knowledge must be sufficient that it would cause any reasonable person to believe that a crime exists, and that evidence is likely to be present at the location.

Example of Reasonable Suspicion Stop

Max is pulled over by a police officer who saw his car weaving on the roadway. The officer asks Max for his drivers’ license, and notices a strong smell of marijuana coming through the open window. Having asked Max to get out of the car, the officer then notices both a strong smell of alcohol on Max’s breath, and tiny green flakes on his shirt. The officer detains Max based on a reasonable suspicion that Max is under the influence of alcohol and drugs.

The officer had reasonable suspicion that a crime was being committed, as he suspected the driver of the car was inebriated because of his inability to drive in a straight line. When the officer smelled the strong and distinctive odor of marijuana wafting out the car window, and saw what looked like marijuana residue on Max’s clothing, he had probable cause that Max was were committing a drug-related crime.

In this example, reasonable suspicion allowed the officer to pull the car over, and to temporarily detain its driver, but that alone did not enable the officer to legally search the car. Probable cause that Max was in possession of illegal drugs – inside the car – gave the officer the right to search both Max’s person, as well as the car, for drugs and paraphernalia.

Reasonable Suspicion in Employee Drug Testing

Another area in which reasonable suspicion may be required. Many employers require prospective applicants to submit to a drug test, and some require periodic or random drug testing throughout employment. Most employers, however, have policies in place to require employee drug testing in only two situations: (1) after an on-the-job accident, and (2) when there is reasonable suspicion that an employee is under the influence of drugs or alcohol.

To protect themselves, many employers require specific documentation of incidents that lead supervisors to suspect that an employee is under the influence. Testing is more commonly done on employees in safe-sensitive jobs, at which accidents could cause serious harm or injury. Employee drug testing is specific to certain illegal substances, which generally include:

  • Marijuana
  • Cocaine
  • Amphetamines (including amphetamine & methamphetamine)
  • Opiates (including morphine, codeine & heroin)
  • Phencyclidine (PCP)

An employer may have reasonable suspicion to require an employee to submit to drug testing when a supervisor becomes aware of the following:

  • Odor of alcohol on the employee’s body or breath
  • Slurred speech
  • Unsteady standing or walking
  • Inability or difficulty completing routine tasks
  • Disorientation or confusion
  • Erratic or unusual behavior

Lack of Reasonable Suspicion Example Lawsuit

In 2012, the American Civil Liberties Union (“ACLU”) file a lawsuit on behalf of Jose Sanchez and the residents of the Olympic Peninsula, in the state of Washington. The lawsuit complains that the U.S. Border Patrol, in this area that is close to the border with Canada, were engaging in the practice of stopping vehicles with no reasonable suspicion, and interrogating the occupants.

Jose Sanchez, a correctional officer at the Olympic Corrections Center, was stopped in his vehicle by Border Patrol agents, who said the tint on his windows was too dark. In fact, his driver’s side window wasn’t tinted at all, and he was asked where he was from. But this wasn’t the first time Sanchez, a U.S. citizen, had been harassed without reasonable suspicion.

Sanchez had previously been stopped, while driving with a family member, and interrogated by the Border Patrol about his immigration status. When asked why he had been pulled over, the agents said his windows were too dark, though they failed to request Sanchez’ registration or insurance. When he provided them anyway, they didn’t even look at them.

Sanchez decided to take control of the situation one day when Border Patrol agents followed him home, then approached him. When they realized that he was recording the encounter on his cell phone, the agents left. When Sanchez tried to file a complaint with the Border Patrol, he was told “We have certain cars that we need to pull over.” This verified the agency’s practice of racial profiling.

In this example of reasonable suspicion not being adhered to, the U.S. Border Patrol settled with Sanchez and the other plaintiffs to the lawsuit in 2013. The terms of the settlement agreement required the Border Patrol to acknowledge that its agents must have reasonable suspicion that a person is violating the law, in order to legally stop or detain him or her. The agency was also required to put their agents through reasonable suspicion training, as well as additional training on the Fourth Amendment protections offered all people.

Related Legal Terms and Issues

  • Due Process – The fundamental, constitutional right to fair legal proceedings in which all parties will be given notice of the proceedings, and have an opportunity to be heard.
  • Probable Cause – Penalties imposed by the court to create incentive to obey the law, or to comply with the rules and regulations.