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Much of criminal law relies on proof by inference. The value of evidence frequently lies in what it suggests as much as what it shows. An outstretched hand in a dark alley is either an illicit drug deal or a handshake; a semi-coherent moan is either encouragement of, or resistance to, a sexual advance; shouted words to "fuck up" a school principal could be either a promise of harm to come or meaningless bravado. In criminal law, fact finders untangle not only what happened, but why it happened, or perhaps more accurately, what the defendant's state of mind was when it was happening. As all other superfluous facts fall away, the question of mental state lingers as a fulcrum around which culpability swings in criminal law. Reaching the answer to the mental state question, however, is a deceptively complex one. The fact finder must engage in an interpretive act, considering not only what can be seen or heard as evidence, but also the significance of that testimonial or physical evidence in real-world contexts-both the world in which the events occurred, and the fact finder's own world. This act of interpretation seeks to give evidence meaning that the law can recognize.

Developments in neuroscience suggest that in the context of juvenile defendants, this moment of interpretation is fraught with particular risks. The emergence of functional magnetic resonance imaging (fMRI) technology has provided significant insights into adolescent brain development and its effect on adolescent thought processes. As a result, scientists (and courts) recognize that adolescent actors are more likely to engage in risky behavior, fail to properly comprehend long-term consequences, and overvalue reward. In short, science has proven what most long suspected: kids think and react differently than do adults.

Although criminal law has long accounted for this difference procedurally, particularly in the creation of an independent juvenile justice system, there has been little exploration of its significance in the realm of substantive criminal law. This Article argues that what is known of adolescent brain development suggests that adult fact finders are poorly positioned to accurately assess a juvenile defendant's state of mind. In short, current treatment of the state of mind element is insufficient and risks inaccurate results. The current approach to assessing mental state relies on judgments by fact finders who, as adults, lack the perspective of those whose actions and words they seek to interpret in the process of judgment- juvenile defendants. Rather than asking adult fact finders to perform the impossible task of placing themselves in an adolescent's mind, substantive criminal law should instead acknowledge the difference in perspective between adults and adolescents. Further, it should permit evidentiary presentation and jury instructions akin to defenses which rely on the defendant's actual, as opposed to imagined, perspective