This case study presents the mock trial of "Martin Miller." There is no question that Martin killed his girlfriend; he admitted to stabbing her in a violent rage. But what is the degree of his responsibility? By virtue of Martin having the MAOA-L gene variant, together with a history of childhood abuse, should his punishment be reduced? This hypothetical case, which requires students to think through the issues rather than simply look up a verdict, is based on actual events and violent behaviors that resulted in criminal charges claimed to be related to MAOA. The MAOA gene and its effect on behavior have been extensively studied, and research results have been introduced as evidence in court cases with differing results. The present case study allows students to explore how behavioral genetic information can be applied to a courtroom situation, and requires them to integrate information from biology, ethics, and the law. Note: Due to the unusual structure of the case, no answer key is available.