The law of self-defense permits the use of deadly force under a strict set of conditions: the threat must be both imminent and unlawful, and the response, both necessary and proportionate. But what of the murkier scenarios where multiple parties, ensnared in the throes of perceived danger, believe themselves justified in their fears? Consider the tragic case of George Zimmerman and Trayvon Martin—where does the law stand when fear is misplaced, and how swiftly can one lawfully escalate to lethal force? Professor Kimberly Ferzan of the University of Pennsylvania School of Law navigates these shadowy waters and others offering her insights into the delicate balance between legal theory and the stark realities of personal safety.