Probable cause consumes much of a law student's criminal law course of study. The amorphous and loaded term has rich significance to United States criminal law jurisprudence. Trying to define the important term succinctly proves challenging.
Probable cause is the set of facts and information learned and discovered through investigation and inquiry that lead a reasonably prudent person to conclude that an accused party committed an offense. That offense may either warrant criminal prosecution of the accused person or the filing of a civil suit or cause of action against him or her. In other words, probable cause is a standard or level of reasonable belief and suspicion, based upon articulable facts, as is required to bring a civil suit or to arrest and commence prosecution in a criminal context. Prior to a person being sued civilly or arrested and prosecuted criminally, the plaintiff in civil court or law enforcement and the prosecutor in criminal court need to have sufficient facts and information that would cause a reasonable person to conclude that the allegations or charges are accurate and true.
Probable cause is more significant in the criminal law context than in civil law proceedings because of the way in which the standard is used. In criminal law, probable cause forms the foundation for searching persons and their property, for arresting them, and for deprivations of civil liberty. First and foremost, law enforcement must have probable cause in order to search a person or that person's property. Additionally, the police must also have sufficient probable cause to make an arrest of a person. Third, in the majority of criminal cases, the court needs to ascertain that ample probable cause exists to believe that a defendant committed the offense prior to a defendant being able to be prosecuted for that particular offense.
On the other hand, a civil case involves no deprivation of liberty and instead may only involve the loss or property. In a civil law context, a plaintiff needs to have sufficient probable cause or basis to bring a claim against a civil defendant. If the plaintiff lacks sufficient probable cause upon which to ground and base a claim, the defendant may be able to bring a case for malicious prosecution against that ill-prepared plaintiff. Courts are also likely to dismiss suits that have insufficient evidence to bolster the underlying allegations and claims, as dockets are clogged with litigants seeking their opportunities to be heard.