Officer Amy arrives at the bank after it's been robbed. She sees broken glass inside the bank. A man claiming to be the manager, is on the scene. He holds what look like broken lock and seems distressed. He tells Amy that a man, approximately 6 feet tall and weighing almost 200 pounds, broke in and escaped with the money in a small brown paper bag. This all happened last night.

Amy's colleagues already arrested few suspects that matched the unusual physical description of the robber and were held in the station all night. But, unfortunately none of them is the robber. There are times when, no matter how long the investigation lasts or how hard the investigators work, the criminal cannot be found. There are also cases where there is a lack of evidence for the police to either find a suspect or make an arrest. Probable cause is the key issue in the arrest process.

Amy is looking for the last person that appears as suspect and matches the description. But, she can't establish probable cause by saying only something like, I just had a hunch that this person was a burglar. She needs to find firm evidence to arrest him.