Crystal Lake Police Officer Petzelt (defendant) pulled over Mayer (plaintiff) for a traffic violation. Sixty-four-year-old Mayer ran, fell, and was injured. Mayer had recognized Petzelt from a previous altercation in which Petzelt “dragged [Mayer] back to the police station ripping his shirt off” for “telling a lie.” Evidence of the previous altercation was excluded at trial. Mayer sued Petzelt for the injuries resulting from the fall in the District Court for the Northern District of Illinois under its diversity jurisdiction. Judgment was entered in Mayer’s favor in the amount of $25,000, but Petzelt was granted a new trial. In the second trial, a general verdict with special interrogatories was submitted to the jury. The jury found in favor of Mayer as to liability, but found that Mayer did not act with due care in one of the special interrogatories. The court entered a judgment notwithstanding the verdict (j.n.o.v.) in favor of Petzelt. Mayer appealed to the United States Court of Appeals for the Seventh Circuit.