During the following 5 years, from 1971 to 1976, more than $3 million of NIJ funds were devoted to the development of body armor. The research and development program was a team effort involving several of the most innovative and technologically advanced private and government organizations in the country. Contractors from the private sector were The Aerospace Corporation and MITRE Corporation. The U.S. Army's contribution included the efforts of Edgewood Arsenal, Aberdeen Proving Grounds, and Natick Laboratories. The Lawrence Livermore Laboratory and the National Bureau of Standards were also involved in the program, as were the Federal Bureau of Investigation (FBI) and the Secret Service.

The development of body armor or bullet proof vests by NIJ was a four-phase effort that took place over several years. The first phase involved testing Kevlar fabric to determine whether it could stop a lead bullet. The second phase involved determining the number of layers of material necessary to prevent penetration by bullets of varying speeds and calibers and developing a prototype vest that would protect officers against the most common threats -- the .38 Special and the .22 Long Rifle bullets. Bullets from 9mm, .45, and .32 caliber weapons were also investigated.

By 1973, researchers at the Army's Edgewood Arsenal responsible for vest design had developed a garment made of seven layers of Kevlar fabric for use in field trials. During this preliminary testing, environmental trials determined that the penetration resistance of Kevlar was degraded when wet. The bullet resistant properties of the fabric also diminished upon exposure to ultraviolet light, including sunlight. Dry-cleaning agents and bleach also had a negative effect on the antiballistic properties of the fabric, as did repeated washing. To protect against these problems, the vest was designed with waterproofing, as well as with fabric coverings to prevent exposure to sunlight and other degrading agents.