The general rule is that to make an arrest, the police must obtain an arrest warrant. However, if an officer has probable cause to believe that a crime has been committed, and there is no time to obtain a warrant, the officer may make a warrantless arrest. An officer also may make a warrantless arrest of persons who commit a crime in the officer's presence.
An invalid arrest is not generally a defense to prosecution. However, if an arrest is unsupported by probable cause, evidence obtained pursuant to the invalid arrest can be excluded from trial.
When an arrest is made, the arresting officer must read the Miranda warnings to the arrestee. These warnings apprise an arrestee of the right to obtain counsel and the right to remain silent. If these warnings are not read to an arrestee as soon as he or she is taken into custody, any statements that the arrestee makes after the arrest may be excluded from trial.
After the arrest, the police must follow certain guidelines during their investigations. For example, if the arrestee requests an attorney or expresses a wish to remain silent, the officers must honor the request and refrain from questioning the arrestee. However, the police may attempt to confirm that they have arrested the right person. They may do so by showing a victim a photo array that includes a picture of the suspect; by arranging a lineup of live persons at the police station, with the suspect included in the lineup; or by organizing a show-up, which is…