Probable cause is a reasonable belief that a person has committed or will commit a crime. For probable cause to exist, a police officer must have sufficient knowledge of facts to warrant a belief that a suspect is committing a crime. The belief must be based on factual evidence, not just on suspicion. The test which the court employs to determine probable cause is whether an objective person of reasonable intelligence would believe that the circumstances indicate that the person arrested or detained has committed a crime.

Sources of Probable Cause

There are four categories of evidence which may establish probable cause:

  • Observation - Information obtained by an officer through observation
  • Circumstantial evidence - Indirect evidence that implies something occurred but does not directly prove it.  The circumstances surrounding the facts can be used to reasonably infer guilt or innocence
  • Expertise - The training of police officers which enables them to identify certain movements, gestures, preparations, or tools as tending to indicate criminal activity
  • Information - Includes statements by witnesses, victims, and informants
  • Sensory – If the officer detects evidence of a crime simply through sight, smell or hearing, the officer has probable cause. This includes the smell of marijuana or other drugs from inside a vehicle.
  • Consent – if the defendant agrees to a search, then probable cause is automatically created

When Can a Search, Seizure, or Arrest Occur?

In general, probable cause must exist before a search, seizure, or arrest by law enforcement. Search warrants and arrest warrants are only issued upon a finding of probable cause, and warrantless searches or arrests must meet the standard of probable cause to be admissible in court.

The motor vehicle is exempted from the search warrant requirement; in other words, police may search a motor vehicle without a warrant. However, police do need probable cause in order to search the vehicle. The police can search any part of the vehicle as long as they have probable cause that they will find contraband or evidence of a crime. Containers inside the motor vehicle, such as boxes, can also be searched as long as the officer has probable cause.

Probable cause is also established if the officer can see evidence of a crime in plain sight. This includes the home, so an officer who sees marijuana on the table while talking to a homeowner can walk right in and confiscate the evidence. The “plain sight” doctrine extends to the other senses, specifically smell or hearing. Police dogs may also conduct searches wherein the evidence discovered is admissible.

Note that in some cases in some jurisdictions, an arrest may foreclose probable cause. For example, if the officer claims probable cause that there are weapons which may endanger the officer are present in the vehicle, arresting the suspect will void the probable cause. If the suspect is handcuffed, the officer cannot claim that the suspect is dangerous and that the officer therefore has the right to search the vehicle for weapons.

What Happens If Searches, Seizures, and Arrests Occur without Probable Cause?

Evidence directly obtained as a result of a search, seizure, or arrest that occurred without probable cause cannot be used in court against a defendant. In addition, evidence that would not have been obtained but for the illegal search, seizure or arrest may also be inadmissible at trial.

How Does Probable Cause by Consent Work?

Police officers can still perform searches even if the defendant does not consent, as long as the police officer had probable cause in other ways. However, if there is no other probable cause, then the defendant’s consent becomes the last possible area of probable cause. If the defendant had withheld consent though, then the police cannot fall back to that consent.

In order to withhold consent, the suspect simply has to say “Officer, I do not consent to any searches.” Repeat if necessary. Do not physically resist the search or even touch the officer. Do not sign any documents without the presence of an attorney.

If you give consent to the search, there is only probable cause for the search in the areas of the search you consent to. For example, you may give consent to the officer to search your bathroom, but only your bathroom. Again, this will not stop the officer from carrying out the search in other areas, but it will remove probable cause by consent. If you tell the officer that he has no consent to search your bedroom, the officer may search anyway, but there is no probable cause by consent if evidence is found.

Do I Need an Attorney?

If you were searched or arrested without probable cause or were accused of a crime, you should speak to a criminal lawyer immediately to learn more about your rights, your defenses, and the complicated legal system.