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A Genetic Defense for Murder?


Fred B. Schnee
Department of Biology
Loras College
Janine M. Idziak
Bioethics Center
Loras College


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.


  • Understand how genes affect behavior; in particular, realize that although genes can influence behavior, they may also be highly dependent on environmental factors.
  • Recognize that genes like MAOA do not predetermine a behavior but rather cause individuals to be more likely to act in certain ways.
  • Recognize that work in science, such as work in biology/human genetics, can have important implications beyond the realm of science.
  • Engage in interdisciplinary integration, drawing on facts and concepts from biology, philosophical ethics, and law, in order to make a decision and justify it.
  • Enhance skills in research, group work, and oral communication.


MAOA; violent behavior; gene x environment; behavioral genetics; genetic defense and the law; free will and responsibility; bioethics; mock trial; warrior gene

Topical Areas

Ethics, Legal issues, Social issues

Educational Level

Undergraduate lower division, Undergraduate upper division, General public & informal education, Continuing education



Type / Methods

Role-Play, Trial



Subject Headings

Biology (General)  |   Genetics / Heredity  |   Science (General)  |   Neuroscience  |  

Date Posted


Teaching Notes

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The following video(s) are recommended for use in association with this case study.

  • Did My Genes Make Me Do It?
    Geneticist Francis Collins considers whether “my genes made me do it” will ever be a good defense in law. Running time: 2:42 min. Produced by The Faraday Institute, 2010.