Raleigh, N.C. — Body armor is credited with saving more than 3,000 law enforcement officers' lives since the 1970s. But as vests became lighter and stronger, tests also raised questions about their longevity.

Many agencies for years didn't place a priority on outfitting officers with up-to-date bullet-proof vests, although the vests are often the last line of protection between officers and armed criminals.

"Officers were borrowing vests or getting used vests, which were totally inappropriate and unsafe," said John Midgette, executive director of the North Carolina Police Benevolent Association. "If it doesn't work properly, it's a safety issue."

The landscape changed after bullets pierced two vests in 2003 – a California officer died, and a Pennsylvania officer was injured. Lawsuits followed, and armor made with the product Zylon were pulled from the market.

"Unfortunately, like in most things, it takes a very critical case to bring that to light," Midgette said.

The state Highway Patrol and other law enforcement agencies started paying closer attention to wear life.

"It was a wake-up call because we want to make sure our troopers weren't wearing equipment that had been deemed unsafe," said Lt. Everett Clendenin of the Highway Patrol.

New armor isn't cheap, with each vest costing from $600 to more than $1,000. Smaller departments qualify for federal matching funds to buy armor.

Al Sutton, president of Lawmen's, a police equipment supply dealer, said most agencies, including the police departments in Raleigh and Durham and the Wake County Sheriff's Office, follow five-year warranty guidelines for replacing vests.

Heat, sweat and normal wear and tear cause the materials in the body armor to break down over time, Sutton said.

"There's not many products that you would wear on a daily basis that would really last or fit or wear properly after five years," he said.

In 2002, the Fayetteville Police Department stuck with older vests as long as they appeared safe. Now, department policies dictate a five-year replacement cycle.

"After the warranty is up, they're still good. It's just we choose not to wear the vests that are not under warranty," Fayetteville Police Sgt. John Somerindyke said.

Last year, Officer Douglas Austin took a bullet to the chest while trying to apprehend two robbery suspects in Fayetteville. He survived the shooting.

Probation officers are some of the last law enforcement officers in North Carolina still wearing older vests, but the state Department of Correction is spending $850,000 to outfit more than 1,500 probation officers with new body armor.