A shocking matter may have been proved to be fact in the American history through a DNA testing, conducted by Dr.Eugine Foster. The alleged affair between Thomas Jefferson, the third President, and his slave, Sally Hemings, may prove to be not just a story but a historical fact. It probably began in 1788, when Jefferson stayed in Paris as an American Ambassador to France. This liaison continued until 1826 when Jefferson died. My hypothesis is that the DNA testing was to allow the story of Jefferson and Hemings to revive in American history, particularly in Black history. In other words, it exposed a nation-wide cover-up, that is, the crime of racial discrimination. In this paper, I argue the details of the DNA testing, and explore the essence of the problems that the Jefferson-Hemings affair has raised.