Kloepfer designed a smart handgun that fires only when a finger it recognizes is on the grip. More than 1,000 fingerprints can be authorized per gun, and Kloepfer says the sensor is 99.999 percent accurate.

A child can’t fire the gun. Neither can a thief — important here in a country in which more than 150,000 guns are stolen annually.

Kloepfer’s design won a grand prize in the Intel International Science and Engineering Fair. Then he won a $50,000 grant from the Smart Tech Challenges Foundation to refine the technology. By the time he enters college in the fall (he applied early to Stanford and has been deferred), he hopes to be ready to license the technology to a manufacturer.

There are other approaches to smart guns. The best known, the Armatix iP1, made by a German company and available in the United States through a complicated online procedure, can be fired only if the shooter is wearing a companion wristwatch.

The National Rifle Association seems set against smart guns, apparently fearing that they might become mandatory. One problem has been an unfortunate 2002 New Jersey law stipulating that three years after smart guns are available anywhere in the United States, only smart guns can be sold in the state. The attorney general’s office there ruled recently that the Armatix smart gun would not trigger the law, but the provision has still led gun enthusiasts to bully dealers to keep smart guns off the market everywhere in the U.S.

Opponents of smart guns say that they aren’t fully reliable. Some, including Kloepfer’s, will need batteries to be recharged once a year or so. Still, if Veronica Rutledge had had one in her purse in that Idaho Walmart, her son wouldn’t have been able to shoot and kill her.

“Smart guns are going to save lives,” says Stephen Teret, a gun expert at the Johns Hopkins Bloomberg School of Public Health. “They’re not going to save all lives, but why wouldn’t we want to make guns as safe a consumer product as possible?”