Stefan Zappey, a former elementary school teacher at a U.S. Department of Defense school in Stuttgart, Germany, was convicted by a jury of multiple counts of aggravated sexual abuse and abusive sexual contact with children under the age of twelve. The victims, now four women, reported that between 2006 and 2010, Zappey molested them during classroom instruction and private reading sessions. The case relied heavily on the victims' memories of events that occurred over a decade prior, with some victims testifying that they did not realize the conduct was abusive until they were older. During the trial, Zappey sought to introduce expert testimony from two psychologists, Dr. Christopher Tillitski and Dr. Jeffrey Neuschatz, to challenge the reliability of the victims' memories. The district court limited Dr. Tillitski's testimony to general topics raised by the government's expert and completely excluded Dr. Neuschatz's testimony. Zappey was sentenced to life in prison and appealed, arguing that the evidentiary rulings prevented him from presenting a complete defense regarding the reliability of the victims' childhood memories.
The Eleventh Circuit reviewed the district court's evidentiary rulings under an abuse of discretion standard, focusing on Federal Rules of Evidence 702 and 403. The court first addressed the exclusion of Dr. Tillitski's testimony regarding eyewitness identification and witness credibility. Citing precedent, the court reaffirmed that expert testimony directly commenting on the weight and credibility of witnesses is impermissible as it invades the jury's province. However, the court distinguished this from general expert testimony on the science of memory reliability, noting that such testimony can be helpful to a jury in cases involving delayed disclosure and childhood abuse. The court found the district court acted within its discretion by limiting Dr. Tillitski to topics raised by the government's expert and excluding portions of his testimony that were cumulative, common knowledge, or effectively an attack on witness credibility. Regarding Dr. Neuschatz, the court applied the 'cumulative' test from Johnson v. United States. It found that Dr. Neuschatz's testimony on false memory construction was duplicative of Dr. Tillitski's extensive testimony, relied on the same evidence, and did not offer a unique perspective or higher qualification. The court concluded that the exclusion of this testimony did not prejudice Zappey, especially given the substantial corroborating evidence from other witnesses, including former teachers and a dental assistant, who testified to Zappey's inappropriate conduct.
The decision affirms the life sentence for Zappey and reinforces the Eleventh Circuit's gatekeeping role in admitting expert testimony on memory science in sexual abuse cases. It establishes that while experts can explain how memory works, they cannot testify to the specific reliability of a witness's memory in a way that suggests the witness is lying or mistaken. Future defendants in similar cases must ensure their experts focus on general scientific principles rather than specific credibility assessments to avoid exclusion. The ruling leaves open the question of how much expert testimony is necessary to assist a jury in cases where memory is the primary evidence, but confirms that trial courts have broad discretion to limit testimony that is cumulative or redundant.