Recently, a new concept of behavior and the law has emerged which looks beyond the defendant's satisfaction of the elements which define the charge. This formulation, which considers not simply the objective facts but motive, intent, and circumstance, has marked a legal shift from diminished capacity to diminished responsibility. Still in evolution, this trend has challenged the relationship between law and the behavioral sciences, and prompted serious reconsideration of the role of each. This paper examines the landmarks of the movement, considers its implications, and looks to the future.