Legal Definitions - probable cause

Probable cause is a Fourth Amendment requirement for police to make arrests, conduct searches, or obtain warrants. It means there is a reasonable basis to believe that a crime has been committed (for an arrest) or that evidence of a crime will be found in a specific location (for a search). This standard is flexible, practical, and based on the totality of circumstances.

Probable cause is a fundamental legal standard that requires law enforcement officers to have a reasonable belief, supported by facts and circumstances, that a crime has been or is being committed, or that evidence of a crime will be found in a particular location. This standard is crucial under the Fourth Amendment of the U.S. Constitution and must generally be met before police can make an arrest, conduct a search, or obtain a warrant from a judge. It's a practical, common-sense assessment based on all available information, rather than a technical or absolute certainty.

• Example 1: Probable Cause for an Arrest

  Imagine police officers respond to a convenience store after an alarm is triggered. Upon arrival, they see a broken window and a person running from the store's back exit, carrying a backpack that appears to be bulging. The person matches a general description given by a passerby who reported seeing someone suspicious near the store minutes earlier. As the officers approach, the individual drops the backpack and attempts to climb a fence.

  How it illustrates probable cause: The combination of the activated alarm, the broken window, the person fleeing the scene, carrying a bulging bag, matching a general description, and then attempting to evade capture, provides the officers with a reasonable belief that this individual has just committed a burglary. This collection of facts and observations constitutes probable cause to arrest the person.

• Example 2: Probable Cause for a Search Warrant

  A detective is investigating a series of car thefts in a neighborhood. A witness reports seeing a specific model of car, known to be a favorite target of the thieves, being driven into a particular garage late at night, with its license plates covered. The witness also notes that the car had damage consistent with forced entry. The detective then checks public records and finds that the garage belongs to an individual with a history of vehicle-related offenses. The detective compiles this information into an affidavit for a judge.

  How it illustrates probable cause: The witness's detailed observation of a suspicious vehicle (matching stolen car descriptions, covered plates, forced entry damage) being driven into a specific garage, combined with the owner's relevant criminal history, provides a judge with a reasonable basis to believe that evidence of car theft (the stolen vehicle itself) will be found inside that garage. This would be sufficient for the judge to issue a search warrant.

• Example 3: Probable Cause for a Warrantless Search (Exigent Circumstances)

  Police officers are on patrol when they hear screams coming from inside an apartment. As they approach the door, they hear sounds of a struggle and a distinct cry for help. The officers also notice a strong smell of burning chemicals emanating from under the door, which is concerning given the potential for a dangerous situation like a drug lab or an assault involving hazardous substances.

  How it illustrates probable cause: The officers have a reasonable belief, based on the screams, sounds of struggle, cry for help, and the smell of burning chemicals, that a crime is actively occurring inside the apartment and that there is an immediate danger to someone's safety or a risk of evidence being destroyed. These "exigent circumstances" (emergency situation) provide probable cause to enter the apartment without a warrant to prevent harm or investigate the ongoing crime.