Public service responses are often frequent in EMS systems and present an opportunity for medical negligence if they are not handled appropriately. These may result from a person calling 9-1-1 because of an inability to get up after a fall. Complicating matters more, a significant number of these responses tend to involve elderly or handicapped persons who may not be able to identify if they are truly injured. A study by Yale University School of Medicine indicates one third of these responses generate a second response to the same address within 30 days, which concludes these calls may be early indicators of medical problems requiring more aggressive evaluation.