After the Kansas-Nebraska Act was passed, Kansas was allowed to choose if they were going to be free or slave. They drafted the Lecompton constitution, this would make them a slave state. However, the government sent it back for Kansas to vote on it. It was rejected and Kansas became free http://americanhistory.about.com/od/civilwarmenu/tp/secessionevents.htm
Dred Scott, a slave, sued his owner for his freedom since he was in a free state. Sadly, Chief Justice Roger Taney denied his freedom saying he was a slave and had no right to sue, right there the case was null and void, but he also realized the Missouri Compromise and the Compromise of 1850 were unconstitutional, they banned slavery in areas which was illegeal according to the 5th Amendment.
Charles Sumner critisized pro-slavery people in Kansas and insulted SC. So, Preston Brooks, a relative of the Senator of SC, walked into Senate and brutally beat Sumner down with a cane until he was unconscious. He was only fined $300.