By the time Dred Scott's case made it all the way to the final outcome at the Supreme Court, it gave about as clear an example as can be of what's wrong with the "original intent" school of constitutional interpretation:
It then proceeds to say: 'We hold these truths to be self-evident: that all men are created equal; that they are endowed by their Creator with certain unalienable rights; that among them is life, liberty, and the pursuit of happiness; that to secure these rights, Governments are instituted, deriving their just powers from the consent of the governed.'
The general words above quoted would seem to embrace the whole human family, and if they were used in a similar instrument at this day would be so understood. But it is too clear for dispute, that the enslaved African race were not intended to be included, and formed no part of the people who framed and adopted this declaration; for if the language, as understood in that day, would embrace them, the conduct of the distinguished men who framed the Declaration of Independence would have been utterly and flagrantly inconsistent with the principles they asserted; and instead of the sympathy of mankind, to which they so confidently appealed, they would have deserved and received universal rebuke and reprobation.
Yet the men who framed this declaration were great men-high in literary acquirements-high in their sense of honor, and incapable of asserting principles inconsistent with those on which they were acting. They perfectly understood the meaning of the language they used, and how it would be understood by others; and they knew that it would not in any part of the civilized world be supposed to embrace the negro race, which, by common consent, had been excluded from civilized Governments and the family of nations, and doomed to slavery. They spoke and acted according to the then established doctrines and principles, and in the ordinary language of the day, and no one misunderstood them. The unhappy black race were separated from the white by indelible marks, and laws long before established, and were never thought of or spoken of except as property, and when the claims of the owner or the profit of the trader were supposed to need protection.
This state of public opinion had undergone no change when the Constitution was adopted, as is equally evident from its provisions and language.
But how did the case get there exactly? And who was Dred Scott anyway?
For the first question, see the excellent web work done by Washington University at St. Louis and the Missouri State Archives.
For the second, you could try this new book, I, Dred Scott, a young adult book written in the form of a first-person slave narrative. I saw it at Branch's Bookshop last night and almost bought it--I may yet.