The Dred Scott decision (from a case formally known as Dred Scott v. Sandford), represents the depths of injustice that have been inflicted upon African Americans using the American legal system. This was a case about slavery and African American rights that was decided in 1857.
Dred Scott was a slave. During his lifetime, he had been brought by his owner into various free states and territories. When his owner died, he sued the owner’s widow to be set free on the basis that his time living in the free parts of the country had made him a free man. This case made its way up through the courts and was decided by the Supreme Court in 1857. This is one of the most vilified decisions in history.
The most important aspect of this decision from a purely African American history point of view is that Chief Justice Roger Taney held that African Americans were not, and could not be, full citizens of the United States. Taney also ruled that Congress could not make laws prohibiting slavery in the territories (those territories had to decide for themselves if they would be free or slave). This nullified the Missouri Compromise and ended attempts at compromise over the expansion of slavery. This helped to bring on the Civil War.
Thus, this case represents injustice towards African Americans as it is a case in which the Supreme Court of the United States ruled that they were not full citizens and therefore did not have any true rights.