WASHINGTON — Lester Shubin, the Justice Department researcher who turned a DuPont fabric intended for tires into the first truly effective bulletproof vests, saving the lives of more than 3,000 law enforcement officers, died after a heart attack at his Virginia home. He was 84.

Shubin was working at the National Institute for Justice, the research and development branch of the Justice Department, in the early 1970s when DuPont came out with a fabric that was to replace steel-belting on high-speed tires.

Nicholas Montanarelli, who worked for the Army’s Land Warfare Laboratory at the Aberdeen Proving Ground, mentioned this new substance, Kevlar, which was said to be “stronger than steel, lighter than nylon.” Montanarelli obtained a couple of samples of what Shubin called “this funny yellow fabric,” and the men took it and some handguns to a firing range.

“We folded it over a couple of times and shot at it. The bullets didn’t go through,” Shubin later told a Justice Department report on the National Institute for Justice’s accomplishments.

Developing armor

Attempts at body armor have been around for thousands of years. Medieval knights clothed themselves head to toe in metal armor. By the World War II era, there were cloth flak jackets with metal inserts.

Kevlar was different; it worked by deforming the bullet, spreading its energy as it hit the body armor. It wasn’t perfect. It protected against 80 to 85 percent of the handguns then on the market, not rifles, and a wearer could suffer bruises or broken bones. But it saved lives.

Shubin went back to the Justice Department to wrest $5 million in research money out of the bureaucracy, and Montanarelli began developing the tests. They wanted their vest to be not only strong but also lighter than earlier versions, and flexible enough so that police officers and soldiers could work in it.

Testing

They put their new vest over a gelatin mold to determine how a human body might react to the impact of a handgun bullet and then drafted, as test subjects, a series of unfortunate goats.

When Shubin and Montanarelli were satisfied with the performance of the body armor, they had to contend with manufacturers worried about getting sued if the products failed.

“That was almost a bigger problem than developing the body armor,” Montanarelli, of Bel Air, Md., said in a phone interview.

Shubin got what was then the National Bureau of Standards to come up with specifications that reassured manufacturers. Using federal money, 500 vests were made to be given away. But many police departments wouldn’t take them, and those that did had trouble persuading street cops to use them — until 1975. That was the year a Seattle police officer wearing a Kevlar vest walked in on an armed robbery in a convenience store and was shot at point-blank range.

He survived to complain about doctors who kept him in the hospital over Christmas Eve because they found it hard to believe that he had only bruises.

Shubin, a native of Philadelphia, served in the Army during World War II and was among the troops that liberated the Dachau concentration camp, said his son, Harry Shubin.