This review examines how advances in neuroscience are affecting civil law, criminal law, and law enforcement. Brain imaging techniques have already been used to detect brain injury, assess pain, and determine mental state and capacity for rational thought. There is also much excitement about using neuroimaging to detect lies and deception in legal and national security contexts. Despite claims of neuroimaging's revolutionary nature, numerous questions should be answered about their validity and reliability before they become widely adopted. Neuroscientists still do not fully understand the link between brain activity and behavior or memory formation. Important legal and ethical questions remain unresolved, particularly around the potential effect on juries and judges of colorful, but scientifically unproven, brain images. Finally, the very impetus behind the use of neuroscience in the legal system—to avoid the subjectivity and uncertainty of more traditional methods for assessing thought and behavior—may ...