Probable cause is a reason to believe that a crime has occurred or that the person's property is related to some sort of criminal activity. In order to make an arrest without a warrant, probable cause must be present. Probable cause is a very important factor in the criminal justice system. No arrest, search or seizure may take place unless based on reasonable belief. Searches carried out without a warrant are considered unreasonable, except in urgent circumstances. Exceptional circumstances occur when there is not sufficient time for an officer to obtain a warrant and action must be taken. Even if the spontaneous nature of the event is unjustifiable, it must nevertheless be probable.