The discussion notes that a police officer is killed in the line of duty every 57 hours and that wearing body armor has saved the lives of 2,700 police officers. The use of armor dates from medieval times. The flak jackets used in World War II relied on metal plates and reduced injuries. The Navy tested synthetics after World War II. The military used still plates in nylon vests during the Vietnam War. Civil disturbances during that period resulted in awareness that police needed more protection. National Institute of Justice researcher Lester Shubin worked during 1971-91 to develop and improve body armor, using the material Kevlar developed by another research chemist in 1964. Efforts focused on developing concealable, lightweight, wearable body armor. The material worked by deforming the bullet and spreading its energy as it hit the body armor. The research determined that 44 millimeters was the depth of the blunt force trauma a human body could sustain without fatality. The early Kevlar body armor was bulky and heavy. A Seattle police officer shot over the heart in 1975 became the first person saved by body armor. Police officers started an organization called the Survivors’ Club to raise awareness of the benefits of body armor. Further research in recognition that vests can fail in some circumstances has aimed to balance protection and performance. Weapons advances and the use of body armor by criminals has resulted in further research, changes in weapons used by police, and efforts to prevent offenders from obtaining body armor. Further developments include efforts to provide body armor for police dogs, efforts to develop body armor to protect against knives, the use of body armor by police in the United Kingdom, and the development of more advanced body armor for SWAT teams. Statements by police officers and case examples of incidents involving police shootings