Stowe provides further details about her story based on actual events in A Key to Uncle Tom’s Cabin.
In A Key to UTC, Stowe cites the ‘not-guilty’ aftermath of an 1847 South Carolina court case and trial regarding a Mrs. Rowand, who killed her slave Maria. [This connection is to the legal and moral consequences attached to Cassy’s thoughts of murdering Legree (not a possibility for her) juxtaposed with Legree’s possibility of killing his slave if he keeps beating his defiance and the future killing of Tom)]:
[Rowand’s lawyer] says, “When punishment is due to the slave, the master must not be held to strict account for going an inch beyond the mark.” And finally, and most astounding of all, comes this: “He bade the jury remember the words of Him who spake as never man spake—LET HIM THAT HATH NEVER SINNED THROW THE FIRST STONE. They, as masters, might regret excesses to which they themselves might have carried punishment.”
And Stowe’s final statement for this chapter:
“And this trial is paraded as a triumphant specimen of legal impartiality and equity! ‘If the light that is in thee be darkness, how great is that darkness!’”
The full story of this connection can be read in Chapter VII, Part II “The Execution of Justice” of A Key to Uncle Tom’s Cabin.
In A Key to Uncle Tom’s Cabin, Stowe tells the story of a young female quadroon, who is in Washington , DC and put in jail as a slave in 1850. Her mother is free in New York City and receives a letter from her daughter, beseeching her to come to DC to help her to freedom. Because Emily is beautiful, she will cost too much money for her mother to buy her. Emily soon dies on a journey with her trader. Emily’s description fits closely with that of the character Emmeline in UTC.
The full story of this connection can be read in Chapter VII, Part III “Emily Russell” of A Key to Uncle Tom’s Cabin.