Legal Foundations and the Criminal Justice System
Sources and structure of law
Arizona officers enforce overlapping layers of law: the U.S. Constitution (especially the Fourth, Fifth, Sixth, and Fourteenth Amendments), the Arizona Constitution (Article II, §8 is the state search-and-seizure clause), the Arizona Revised Statutes (ARS), county and municipal ordinances, and case law from the U.S. Supreme Court and Arizona appellate courts. Know the court map: municipal and justice courts handle misdemeanors and initial appearances; superior courts handle felonies and civil matters; the Court of Appeals is intermediate; the Arizona Supreme Court is the final state court.
Standards of proof
Questions love to blur the standards. Reasonable suspicion is a particularized, articulable basis for a stop. Probable cause is a fair probability that a crime occurred or that evidence is in a particular place. Preponderance is more likely than not; clear and convincing is higher; beyond a reasonable doubt is the criminal trial standard. Miranda warnings are triggered by custody plus interrogation-not by questioning alone.
Common traps
- “Miranda applies whenever police question someone” - false; it is custody plus interrogation.
- “A hunch is reasonable suspicion” - no; you must articulate specific facts.
- “An unlawful stop ruins only the stop” - the exclusionary rule can reach derivative evidence under the fruit-of-the-poisonous-tree doctrine, subject to exceptions such as attenuation, independent source, and inevitable discovery.
Rule of thumb
Write reports as if a judge will ask, “What did you know, and when did you know it?” For every detention, name the specific facts-time, place, behavior, furtive movements, matching description-that made suspicion reasonable.