Mayor Martin J. Walsh was quick to announce a gun buyback program after a 9-year-old boy was shot dead in Mattapan on Friday but an expert warns that strategy will do little to curb violence in the Hub.

Gun buyback programs have been tried for years in cities around the world, including in Boston, but studies show the weapons recovered typically aren’t the ones used in homicides.

“Most of the guns that are used in crimes are fairly new, large caliber semi-automatic pistols,” said Thomas Nolan, a former 27-year Boston cop who teaches criminal justice at the State University of New York at Plattsburgh. “The majority of what you see in these gun buyback programs are revolvers. We don’t even know if these guns are capable of being fired.”

Buyback programs offer people money or gift cards for their guns, turned in anonymously. Such programs, while they have been conducted for years, gained new popularity after the 2012 Newtown, Conn., school shooting. Boston’s last buyback, in 2006, offered $200 Target gift cards for each gun and netted 700 weapons.

Nolan noted that people involved in violent crimes are the least likely to surrender their weapons.

“This is a little bit gimmicky,” he said. “They’ve done them all over the country, but I think in 2014 we should be thinking of entirely new means of addressing these issues rather than recycling old and somewhat tired ideas.”

But Nolan added that a buyback is worth the money if it prevents even one homicide.

Dr. Robert Sege, a pediatrician at Boston Medical Center who studies gun violence, said, “This tragedy that happened on Friday clearly requires a response, and a gun buyback program is something we can do. The main thing gun buybacks do is send a message that we don’t need to have guns in our home. These are guns that could be stolen or used for crimes.”

Walsh has yet to announce any details of his proposed buyback program.

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