Did Thomas Jefferson, third president of the United States, have children with his slave Sally Hemings? This PowerPoint clicker case explores this controversial question as students consider the evidence for Jefferson as the father of Eston Hemings, as well as the limitations of that evidence. In the process, students learn about Y-chromosomal and mitochondrial DNA and how they are passed down through generations. They also learn about the role of genetic tests in examining family lineages. In addition, the case serves to illustrate how science cannot always provide a direct and definitive answer and how conclusions often must be based on a mixture of scientific and historical (or other) evidence. The case was designed for an introductory biology course for non-majors but could easily be adapted for a majors' course or for the introductory portion of a genetics course. Students should have some prior knowledge of chromosomes and hereditability.