It is fairly common for a person facing criminal charges in Iowa to have prior criminal convictions. If the defendant is ultimately convicted of the charges they are currently facing, those prior convictions can result in an increased sentence. But can those prior crimes be introduced at the trial, as evidence of defendant's guilt in the case presently before the court?
The answer depends in part on the purpose for which the evidence of prior crimes is offered. Both the Federal and Iowa Rules of Evidence prohibit the prosecution from introducing prior crimes as character evidence, to show the defendant acted consistently with their character. Prior crimes can be introduced for specific purposes, such as to show intent, opportunity, motive, plan, preparation, identity, knowledge, or lack of mistake or accident.
For example, if a defendant is accused of committing armed robbery of a convenience store, and a witness says the perpetrator was wearing an orange wig at the time of the robbery and locked the employees in the cooler before fleeing, evidence that the defendant committed an armed robbery two years earlier, in which he wore an orange wig and locked employees in the cooler, may be admissible to prove identity.
Similarly, if the defendant is on trial for murder, evidence that the defendant previously assaulted the victim may be admissible to prove intent or motive. Evidence that the defendant previously assaulted another person would likely be inadmissible, if it was offered only to show the defendant had a violent disposition. On the other hand, if the defendant offered evidence that he or she had a nonviolent disposition, the prosecution could introduce the previous assault to rebut that contention.
Admissibility of prior crimes is often a hotly contested issue in criminal trials. When a jury hears that a defendant has been accused of committing similar offenses in the past, it can lead them to abandon the presumption of innocence and assume the defendant is guilty in the crime for which he is currently on trial. Thus, it is crucial for the defendant to understand what is potentially at stake when the prosecution tries to admit this kind of evidence.
Source: Iowa State Legislature, "Iowa Rule of Evidence 5.404(b)," accessed Jan. 28, 2017