Scott's lawyers used an argument based on the fact the defendant—Sanford—and the plaintiff were from different states, shifting the focus of the case to whether the Supreme Court had jurisdiction and whether or not Scott was a citizen of the United States.
In 1846, after Emerson died, Scott sued his master's widow for his freedom on the grounds that he had lived as a resident of a free state and territory. He won his suit in a lower court, but the Missouri supreme court reversed the decision.
Irene Emerson became the owner of the Scott family. Her brother, John Sanford, took responsibility for Irene Emerson's property and advised her on financial matters. Since Sanford knew that the Scotts' status as slaves was open to question he may have advised his sister that it would be unwise to attempt to sell them.
Lincoln interpreted the Dred Scott decision and the Kansas-Nebraska Act as efforts to nationalize slavery: that is, to make it legal everywhere from New England to the Midwest and beyond.
John Brown was a man of action -- a man who would not be deterred from his mission of abolishing slavery. On October 16, 1859, he led 21 men on a raid of the federal arsenal at Harpers Ferry, Virginia.
On April 6th, 1846, Dred Scott and his wife Harriet filed suit against Irene Emerson for their freedom. It is not known for sure why he chose this particular time for the suit- for almost nine years, Scott had lived in free territories and had the standing to legally challenge his enslavement.
After the fighting ended, Emerson went to the Iowa Territory, but the Scotts remained in St. Louis, where they apparently hired out their services to various people. In December 1843 Emerson suddenly died, leaving his estate—including the Scotts—to his widow.
Why did Dred Scott believe he should be freed? He believed that when his previous owner took him to lands in the upper Louisiana Purchase and Illinois that he was considered free.