This article outlines how to incorporate argumentation into a forensic science unit using a mock trial. Practical details of the mock trial include: (1) a method of scaffolding students' development of their argument for the trial, (2) a clearly outlined set of expectations for students during the planning and implementation of the mock trial, and (3) an example of how to use questioning to guide students through the planning of the mock trial. While a general forensic science unit is provided in the article, a teacher can use the details of the mock trial with any forensic science unit for either middle school or secondary science students.