When Latonya Lester (plaintiff) was four-years old, she was struck by a truck and severely injured while she was crossing a wet street in St. Louis, Missouri. The truck that struck Lester was being driven by Mark Sayles (defendant). Lester sued Sayles for negligence in state court in Missouri, and a jury found for her and awarded damages. On the day of trial, Sayles moved for leave to appeal his answer to allege Lester’s comparative negligence, which the court denied. After judgment, Sayles appealed and alleged reversible error in the trial court’s denial of his motion to amend his answer and its failure to instruct the jury that it could assess Lester’s fault.