The rules of evidence generally prohibit the use of “evidence of other crimes, wrongs, or acts” to prove someone’s character to show that the person acted in conformity with their character. Other crimes, wrongs or acts can be admitted to prove such things as motive, opportunity, intent, plan, knowledge, identity, or absence of mistake or accident.[i] The jury instruction on “other-acts” evidence concludes: “You may not consider this evidence to conclude that the defendant has a certain character or a certain character trait and that the defendant acted in conformity with that trait or character with respect to the offense charged in this case.”
This evidentiary rule has generated more confusion than most rules within the legal community among jurors, lawyers, and judges. I believe the reason for the confusion is that the rule works against how humans actually make many decisions, and the stated exceptions to the rule can be read to essentially negate the rule. However, I also believe the rule is needed to provide a fair trial of factual issues.
The rule is attempting to proscribe evidence that one has a certain character and then acted in conformity with this character. Character is defined as the aggregate of features and traits that form the individual nature of some person or thing; or any trait, function, structure, or substance of an organism resulting from the effect of one or more genes as modified by the environment.[ii]
One cannot stare into someone’s eyes and divine a person’s character. The only way to judge a person’s character is to observe the individual’s behaviors and then inductively construct it. For example, one considers that the person was convicted of burglary in the past, and then one reasons that this person has the character for dishonesty and thievery when he or she is confronted with a certain set of circumstances.
To speak about someone’s character and acting in conformity with the character, one must think of a human as some sort of a probabilistic input/output device. First, based on the prior behavior of the subject individual, the evaluator must infer someone’s character. Then one must assume that if someone has this type of character, that when confronted with a set of environmental stimuli, he or she will be more likely to act in a certain way, i.e. provide a certain output, than an individual without that character.
For example, the probability to commit a burglary is a function of the probability that a person will be confronted with the environmental stimulus to burgle multiplied by the probability that one has the character to burgle if confronted with such environmental stimulus. Research shows that the probability that a person with a history of committing crimes or involving themselves with other anti-social behavior will commit another crime is higher than for a person without such history. Therefore, the character evidence of a history or prior convictions or other anti-social activity is evidence that tends to make more probable the defendant’s guilt than a person without such history.[iii]
However, the Wisconsin Supreme Court has stated that: “Evidence of other crimes and misdeeds is not excluded because of an inherent lack of probative value, but is withheld as a precaution against inciting prejudice.” The Court further held that two reasons that character evidence is excluded are: “The over strong tendency to believe the defendant guilty of the charge merely because he is a person likely to do such acts” and the “tendency to condemn not because he is believed guilty of the present charge but because he has escaped punishment from other offenses.”[iv]
Humans make decision based on heuristics—rules that make difficult decisions easier. One such heuristic is that people have character and act in accordance to that character. People say: “Don’t trust Joe, because he is a crook.” They avoid Joe and don’t get hurt and the warning seemed to work, although they probably wouldn’t have gotten hurt if they had trusted him. This heuristic is a quick and easy way to avoid problem individuals. It is related to the same heuristic that classifies people by such things as race, sex, national origin, and all other such classification schemes that are many times erroneous, and often pernicious.
Coupled with this heuristic is the human inability to accurately calculate probabilities. The additional probative value of the character evidence is probably far less than what most people imagine. For most people, knowing someone has been convicted of a crime in the past, feels like strong evidence against that person in another accusation. A defendant with a history of criminal offenses is more likely to offend than someone who doesn’t have that history, but most of the people with a prior conviction will not re-offend. And predictions of whether or not a defendant has committed a crime, often based on merely one past crime, will often be wrong. The additional probative value of “other-acts” evidence on the question of whether or not a defendant re-offended is, in most cases, relatively low.
Also, as emotions are central to human decision making and not separate from them, any emotional response elicited from the “other-acts” evidence (or for that matter any evidence) in a criminal case will impact the likelihood of conviction. Anyone with any experience trying cases understands the need for an emotional edge to win a case. Emotions often lead the rational thought process.
Humans also have an innate need to punish actions that result in harm and wrongful acts. If a defendant had not been punished (or in the eyes of the jury insufficiently punished) for the other bad acts, then the potential risk that a jury would convict a defendant because of unpunished “bad-acts” is greater than if these acts already had been sufficiently punished.
The exceptions to the exclusion of “other-acts” evidence attempt to confine their use to situations where the “other-acts” evidence has a great deal of probative value on an issue of the trial other than just propensity evidence. But when one starts getting into issues such as general motive and intent, it is easy, and often inevitable to slide or plop, into propensity evidence. According to the jury instructions motive refers to a person's reason for doing something and intent is whether the defendant acted with the state of mind required for the offense.
For example, in a child sexual assault case, the State will argue that the defendant’s motive for touching a child was “to obtain sexual gratification from a child”, and his intent was to become sexually gratified, and that a prior similar sexual assault of a different child is admitted into evidence to prove both. The jury instruction on “other-acts” tells the jury that the prior act can only be used on the issues of motive and intent. Why is the prior act probative of the issue of motive and intent? Because of the argument, if he did it before, it is more unlikely that the touching was inadvertent or accidental due to the “law of chances”. If such touching happened once, it may have been from an unlikely, inadvertent or accidental touching. However, if it happened twice, the probability of an inadvertent or accidental touching on both occasions becomes much more unlikely.
If the defendant’s touching wasn’t inadvertent or accidental, then why did the defendant touch the child? Because the defendant touched the child to intentionally obtain sexual gratification. As intent is an element of the crime, the other-acts evidence is certainly being used to prove that the defendant acted in conformity with his character (being sexually attracted to children) with respect to the offense charged. The issues (not to mention the jury instruction on “other-acts”) get muddied and contradictory quite quickly.
If the “other-acts” evidence is offered for, and relative to, an acceptable purpose, then the Court weighs whether or not the probative value of the evidence is substantially outweighed by things such as unfair prejudice or confusion of the issues. The inclusion or exclusion of “other-acts” evidence is ultimately a balancing between allowing a jury to hear evidence that will more likely lead them to a finding of guilt when, without the evidence, it would not make that finding, or excluding the “other-acts” evidence resulting in the jury being more likely to acquit, when with the evidence, it would have found the defendant guilty. The rules regarding “other-acts” evidence, like many of the rules in the criminal justice system, involves a choice between type one error, which is a convicting a defendant for a crime he or she didn’t commit, and type two error, which is acquitting a defendant when in fact the defendant was guilty.
Based on research regarding human decision making, the human need to punish, the inability of humans to correctly assess probabilities, and the uncertain assessment of the probability that a defendant actually committed a crime based on the defendant’s past, it is essential that the trial court act as the gatekeeper to the evidence a jury hears, to ensure that a fair assessment of the facts will be made by the jury. The danger of unfair prejudice urging a conviction despite the evidence is heightened under the circumstances where the “other-acts” evidence ignites the desire to punish, specifically in those instances of “other-acts” conduct that are inordinately heinous, especially relative to the charged conduct, and where the “other-acts” conduct was unpunished or insufficiently punished. The trial court has the power and tools to limit and circumscribe the use of “other-acts” evidence—to allow what facts are necessary to prove the purpose for the evidence, but to exclude those facts that may arouse the human desire to punish and that may prevent factual issues from being fairly determined.