The Supreme Court decision in the Dred Scott case: living in a free state did not make a slave free. 5th Amendment due process protected property, including slaves. Dred Scott was a slave and could not sue in court.
A major source of controversy, the Dred Scott ruling heightened tensions surrounding the subject of slavery in the United States. In the years preceding the American Civil War, it widened the gulf between the states in the North and the South even more.