Dred Scott (1799-1858) was a slave in Missouri and from 1833 to 1843, he traveled with his master, John F. A. Sanford, to the free state of Illinois and the Louisiana territory. Returning to Missouri, Scott sued Sanford, arguing that he was made a free man as he was residing in areas declared free according to the Missouri Compromise of 1820. After a 7-2 decision announced in 1857, the Supreme Court held that African Americans were not, and never were, citizens of the United States according to the Constitution. Therefore, Scott did not have standing to sue in a federal court. Furthermore, the majority held that slaves were property under the Fifth Amendment, and that any law that would deprive a slave owner's property is unconstitutional. The case caused an uproar and resulted in a further polarized the national debate over slavery.
The Supreme Court's ruling was based on the standard of precedent while the debate over slavery had already been ongoing.
[P1] The Supreme Court made its ruling based on the belief that slaves were not qualified to be or become citizens. [P2] The Supreme Court's ruling did not settle the national debate of slavery, but instead intensified it.