Derived from the Latin forensis, the word “forensic” refers at root to “forum.” Forensic is thus the art of the forum—the practice and skill of presenting an argument before a professional, political, or legal gathering. Forensics is in this sense part of rhetoric, which concerns speech. However, it includes not only human speech but also that of things. Because objects cannot actually speak, there is a need for a “translator” or an “interpreter”—a person or a set of technologies to mediate between the thing and the forum. This was the role of the rhetoricians who used a technique that the Greeks and Romans called prosopopoeia—a mode of speaking on behalf of inanimate objects—and it is now the role of the scientist as expert witness.