Courts are often asked by plaintiffs’ counsel to admit evidence of other similar incidents (OSI) in order to show a defendant’s knowledge of an alleged defect, and/or causation. Plaintiffs have used this approach to tap into the power of strength in numbers and will typically seek to introduce evidence of as many “similar” incidents as a trial court will allow. Although the law allows for the introduction of this type of evidence, a trial court must carefully balance the relevancy of this evidence versus the prejudicial effect. The Eighth Circuit in Adams v. Toyota Motor Corp. recently examined the admissibility of evidence of other similar instances in an automotive “unintended acceleration” case. Plaintiff Koua Lee was driving his 1996 Toyota Camry on the highway. While exiting the highway, the car continued to accelerate, failing to stop as he pressed on the brake. Lee rear ended a car stopped at a red light, killing three of the five passengers in the stopped car and severely injuring others, including passengers in his own car. The Court of Appeals, in upholding the trial court’s decision to admit this evidence, affirmed that evidence of substantially similar incidents can be admitted in appropriate circumstances, and that the trial court is in the best position to determine whether or not this evidence is a distraction to jurors or is otherwise unduly prejudicial.

Weighing in favor of admissibility, OSI evidence can be relevant in that it can show a party had notice of defects. It may also be used to demonstrate the magnitude of the danger and the product’s lack of safety for its intended uses. But there are limitations to the use of OSI evidence. The prior incidents must be “substantially similar” to the incident in the case at hand. And the probative nature of the evidence must outweigh its potential for prejudice.

Here, the Court explained that there are no hard and fast rules to determine if the evidence is substantially similar. It is a case by case determination, and the court must focus on all the circumstances surrounding the OSI evidence and the facts of the case. When OSI evidence is admitted, a defendant is free to argue to the jury the evidence is not persuasive by pointing out the dissimilarities between the purported “similar” incident, and the incident presently being litigated.

In determining that there was no abuse of discretion in admitting this evidence, the Court stated the trial court properly looked at the circumstances surrounding the OSI evidence and that evidence was similar to what happened to plaintiff. Each witness drove a 1996 Camry with over 100,000 miles. Each witness testified that the Camry accelerated or maintained speed when his foot was removed from the gas pedal and the brakes were ineffective. Testimony from these three witnesses was very similar to testimony from the plaintiff. Additionally, an expert witness reviewed the OSI evidence and testified that he considered the three witnesses’ experiences to be similar to the plaintiff’s experience. The appellate court also approved of the trial court’s exercise of cautious discretion in limiting the OSI testimony to three witnesses.

There is a risk of admitting OSI evidence. As the Court noted, it can lead to a confusion of issues or be more prejudicial than useful. However, the trial court is in the best position to make sure that this does not occur. As long as the trial court does not abuse its discretion, the admittance of OSI evidence will be upheld.