Assess students' recall of the core holdings and constitutional principles established in four landmark U.S. Supreme Court cases—Marbury v. Madison (judicial review), Brown v. Board of Education (school segregation unconstitutional), Miranda v. Arizona (Miranda warnings and Fifth Amendment rights), and Gideon v. Wainwright (right to counsel under the Sixth Amendment). Identify each case by name, state its primary holding, note the relevant constitutional provision, and give a one-sentence statement of its significance.