Dred scott was an enslave the property of Dr John Emerson who was a surgeon for the army and would have to move to places for his surgery's and took Scott with him.
11 years later it went to supreme court
weather you are free or slave you are not a citizen
But unfortunately Dr Emerson passed away and Scott was left living on free territory.
After his death Scott went to Missouri i court and sued for his freedom because since he was free and living on free territory and the Missouri court let his case win but the Missouri court needed to decide three things.
One was was where is Scott was a citizen or not.
Another thing was to decide if him living in free territory made him free