Prince George’s County police have launched an initiative to track down and prosecute people who sell illegal weapons that could end up in the hands of violent criminals.

“The reality is, if you want to do something about violent crimes, you do something about the guns,” Deputy Chief Hank Stawinski said Monday as he announced the program.

To start, the county police department — which last year collected 1,200 unregistered guns that were found at crime scenes or abandoned — will spend the next 90 days focusing on recovering illegal firearms.

Ordinarily, Stawinski said, the process stops there. Someone illegally carrying or using a gun may be charged, but the gun itself is not investigated further. Now, the department will use a variety of forms of evidence to trace the gun back to its previous owners: the recovered guns’ serial numbers, ballistics tests to match a gun to any open cases in the county, and interviews of the people caught with the guns.

“We want to increase the amount of data we have about guns to make it easier to find the common hands through which they passed,” Stawinski said. He said that the department’s preliminary use of this strategy has already led it to several people who police suspect have brought numerous illegal guns into the county. Those investigations are ongoing, and the suspects have not been charged with gun trafficking.

Although violent crimes have been on the decline in the county, police said most of the people slain in Prince George’s are killed by guns. Last week, a man was shot in his Capitol Heights apartment and relatives said his 5-year-old daughter witnessed the slaying.

Daniel Webster, the director of the Center for Gun Policy and Research at Johns Hopkins University, provided advice to county police on their plan. He praised the registry in Maryland that keeps track of every legal gun sale in the state as a key background ingredient. “All they have to do is punch in that serial number and the make and model of the gun, and presto,” he said. After that, police can interview the person who first legally bought the gun to try to determine how it made its way to unlawful hands.

Webster also mentioned a new state law that will require owners to report the loss or theft of a firearm, starting in November. And Prince George’s started a registry last summer that tracks people convicted of gun offenses.

Webster said police departments rarely pursue gun traffickers aggressively because the sentences for convicted traffickers are generally short. “For most police departments, they view their principal responsibility as putting people in jail who shoot people or commit crimes, as opposed to people who gave them the gun,” he said.

He praised Prince George’s for dedicating resources to an unusual effort.

“In my opinion, they’re very serious offenses when you’re putting lethal weapons into the hands of people who kill and maim and terrorize communities,” Webster said.

Violent crime has been dropping in Prince George’s since 2010. This year, Stawinski said, 17 percent less violent crime has been reported than at the same point a year before.

Stawinski described the gun-trafficking push as an effort to prevent future crimes. “The hope is that we actually make the drop more robust, as well as lasting,” he said.