Habit, Character and Probabilistic Behavior - Debunking Statistical Probability from an Evidentiary Perspective

It is a fundamental rule of Evidence that a person's propensity to act a certain way, shown by his or her past actions, cannot be used as evidence as proof that the person acted consistently with this propensity at the time of the event being litigated. For reasons discussed in this article, this “character evidence”, although probative, is generally not conducive to leading the trier-of-fact to an accurate result. Although the character evidence ban, even considering its exceptions, may be too stringent in excluding very probative evidence, it is accepted in all jurisdictions. Yet, sometimes judges apparently chafe under the bonds of this rule. This is where they may turn to another rule, the rule allowing the introduction of “habit evidence”. If past behavior can be labeled as indicative of “habit” rather than “character,” the evidence now becomes admissible. That this mere shift in nomenclature serves to make the inadmissible admissible is a serious problem that must be addressed. It is not uncommon for courts, applying a less than rigorous “probability analysis” to conclude that several past similar acts are sufficient to establish the actor's “habit” to act in a certain predictable way. This approach inevitably indicates a failure to distinguish inadmissible propensity (character) evidence from admissible habit evidence. The failure to define habit evidence in a way that would distinguish it from character evidence has simply allowed many courts to admit through the back door – the “habit evidence” door – what is forbidden to enter through the front door – “character evidence.” A review of the rules governing the admissibility of habit and character evidence, as well as the review of the judiciary's application of same indicates an incoherent application of what constitutes evidence of habit and/or character evidence. Although both habit and character are driven by human psychology, the rules of evidence pertaining to habit and character evidence appear to be jurisprudentially driven by a superficial understanding and application of statistical probability theory. Such a superficial understanding and application of probability theory has muddied the waters with respect to understanding the distinction between the inadmissibility of character evidence and the admissibility of habit evidence. While probability analysis has a place in the analysis of credible evidence, it has failed with respect to aiding courts in their determination of whether certain conduct rises to the level of habit (and therefore is admissible). Certainly, probability analysis, if performed properly, is a method by which habit, in the “psychological” sense ultimately may be proven. However, as is often the case with respect to the jurisprudential application of the two rules of evidence, a simple finding of repetitive conduct within a less than rigorous statistical context is not the same as finding “habit” from a psychological sense. It is from this perspective that this article concludes that only a “psychological” definition of habit (as opposed to a “probability” definition) can distinguish conduct of a habitual nature from that which is merely character in nature. The law of habit and character is in need of reform. Reform, however, requires an empirical understanding of statistical probability in order to discern the best definitional approach. This article demonstrates that the jurisprudential application of an overly simplified and often misunderstood theory of probability has led to a confounded and incoherent practice of admitting evidence as “habit” when such evidence is otherwise inadmissible as “character.” We ultimately suggest the adoption of a definition of habit evidence that restricts this term to a history of virtually identical uncontemplated reflexive acts that makes repetition almost certain. Although we conclude that probability analysis is not the appropriate construct for defining the existence of habitual behavior, it may nonetheless have a place with respect to discerning otherwise probative evidence consisting of a repetitive nature.