Summarize the supreme court case of dred scott and how it affected the debate about slavery?

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In March 1857, in one of the most controversial events preceding the American Civil War (1861-65), the U.S. Supreme Court issued its decision in the case of Dred Scott v. Sanford. The case had been brought before the court by Dred Scott, a slave who had lived with his owner in a free state before returning to the slave state of Missouri. Scott argued that his time spent in these locations entitled him to emancipation. In his decision, Chief Justice Roger B. Taney, a staunch supporter of slavery, disagreed: The court found that no black, free or slave, could claim U.S. citizenship, and therefore blacks were unable to petition the court for their freedom. The Dred Scott decision incensed abolitionists and heightened North-South tensions, which would erupt in war just three years later

What does this mean lol.