Peter Plaintiff was walking down the sidewalk next to Dagmar’s Microbrewery. As he passed under an open window on the second floor of the brewery, Peter was hit by a falling barrel that caused serious injury to his head and arm. Peter filed a negligence action against Dagmar’s Microbrewery. At trial, Dagmar’s Microbrewery admits that the barrel was from the microbrewery and that Dagmar’s Microbrewery owed a duty of care to others under negligence law. Peter also offers evidence of his injuries and medical expenses. Peter was unable to offer any other evidence. From the answer choices below, what additional evidence would be most helpful to completing Peter’s negligence claim?