Law and science intersect in many arenas. For instance, an Internet search containing the words “law” and “science” immediately produces countless results ranging from playful “Law School vs. Med School” blogs, to more substantive law and science pairings including interdisciplinary “Law and Neuroscience” research efforts and various “Law and Science” periodicals. Despite this apparent connection between the two fields of study, it has resulted in a great deal of debate, particularly when science enters the courtroom. Nevertheless, the use of neuroscience evidence is on the rise, as indicated by a doubling of cases in the United States involving neuroscience evidence from 2006 to 2009. Given the already-existing utilization of (and attempts to use) neuroscience evidence for various legal purposes in jurisdictions throughout the United States, one can expect Louisiana to encounter more lawyers offering such evidence shortly. Therefore, it is important for lawyers and judges in Louisiana to be familiar with the contexts in which this type of evidence is likely to arise and understand how courts have been and ought to be treating it. Accordingly, with a focus on Louisiana, this Comment explores the burgeoning discipline of law and neuroscience by analyzing the multifaceted difficulties of offering neuroscience evidence for purposes of supporting claims of mental incompetency to rescind a contract and claims of insanity to avoid criminal responsibility. This Comment argues that neuroscience evidence in its current stage of development has little utility with regard to proving contractual incapacity and criminal insanity. In addition to these specific claims, this Comment analyzes more general concerns relating to the use of functional neuroimaging in any legal context: the difficulty in assessing a legally defined mental state, the uncertainty involved in generalizing the results of neuroimaging tests to real-world behavior, and the potential prejudicial effects of neuroimaging evidence on a jury.