Iowa Constitution’s Due Process Clause Bars Propensity-to-Commit-Crime Evidence

State and federal evidence rules generally bar the prosecution from introducing evidence of defendant’s past crimes to show a propensity on the defendant’s part to commit similar crimes. If, for instance, the defendant is charged with child molestation, the prosecution can’t introduce evidence that defendant had molested other children to show that defendant likes molesting children and therefore to support the prosecution’s claim that he molested this child.

Past bad act evidence may be introduced for other purposes, such as to show motive (e.g., the defendant killed this victim because the victim witnessed another killing by defendant and was thus a threat to the defendant). But it may not be introduced simply to show propensity to commit this crime, even if it is relevant to do that (for instance, because it shows that defendant likes to commit such crimes, and thus is more likely than the average person to commit the crimes). And this isn’t just a rule of sufficiency of the evidence (i.e., that propensity evidence isn’t enough to prove guilty beyond a reasonable doubt) — it makes the evidence inadmissible even as one part of the prosecution’s broader case.

But that’s generally just a statutory or common-law rule, and many legislatures have changed it by statute in certain ways, especially for sex crimes. Iowa Code § 701.11, in particular, provides that,

In a criminal prosecution in which a defendant has been charged with sexual abuse [defined later in the section -EV], evidence [that constitutes clear proof] of the defendant’s commission of another sexual abuse is admissible and may be considered for its bearing on any matter for which the evidence is relevant. This evidence, though relevant, may be excluded if the probative value of the evidence is substantially outweighed by the danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay, waste of time, or needless presentation of cumulative evidence.

But in State v. Cox, decided April 30, the Iowa Supreme Court held that the admission of such propensity evidence violates the Iowa Constitution’s Due Process Clause. “The policy against admissibility of general propensity evidence stems from ‘a fundamental sense that no one should be convicted of a crime based on his or her previous misdeeds.’ ‘A concomitant of the presumption of innocence is that a defendant must be tried for what he did, not for who he is.’ This concept is ‘fundamental to American jurisprudence.’” In this, the court departed from the view of federal courts and most state courts, and adhered to the minority view, which until then apparently was followed only by the Missouri Supreme Court.

An interesting decision; I’m not sure it’s right, but I wanted to pass it along. Since it interprets the Iowa Constitution, the U.S. Supreme Court can’t review it, though Iowans could amend the constitution if they disapprove of this decision.