A cite for ya RandomLetters. From Here Note: Pro-gun site.
"In the mid 1960’s, Dr. Paul Kopsch (an Ohio coroner), Daniel Turcos (a police sergeant) and Donald Ward (Dr. Kopsch’s special investigator) began experimenting with special purpose handgun ammunition. Their objective was to develop a law enforcement round capable of improved penetration against hard targets like windshield glass and automobile doors. Conventional bullets, made primarily from lead, are often ineffective against hard targets especially when fired at handgun velocities. In the 1970’s, Kopsch, Turcos and Ward produced their “KTW” handgun ammunition using steel cored bullets capable of great penetration. Following further experimentation, in 1981 they began producing bullets constructed primarily of brass. The hard brass bullets caused exceptional wear on handgun barrels, a problem combated by coating the bullets with Teflon. The Teflon coating did nothing to improve penetration, it simply reduced damage to the gun barrel.
Despite the facts that “KTW” ammunition had never been available to the general public and that no police officer has ever been killed by a handgun bullet penetrating their body armor, the media incorrectly reported that the Teflon coated bullets were designed to defeat the body armor that law enforcement officers were beginning to use. The myth of “Cop-killer” bullets was born." [emphasis mine]