A new nationwide push is changing the way officers collect evidence in an effort to solve violent crimes by connecting them, but the News4 I-Team found some departments aren't doing it — even though it could help solve crimes in neighboring cities.

"Gun violence is the most difficult thing that we have to deal with," said Metropolitan Police Department Chief Peter Newsham.

With 160 murders in D.C. last year, he knows the value of strong evidence. That's why his officers are required to pick up every shell casing, even if the call was just for sounds of gunfire. Years ago, that wasn't the case.

"If you arrived on the scene and nobody was injured and you didn't have a crime, then you would clear the scene with no report. Now, we handle it completely differently," said Newsham.

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It's called comprehensive collection. The federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) calls D.C. one of the nation's leaders in doing it.

Every casing goes into the National Integrated Ballistics Information Network (NIBIN). Experts compare 3D images side by side with casings already in the system and tie crimes together. Every gun leaves unique markings, so the outside of a cartridge casing reads like fingerprints for the gun that fired it.

When a gun is found on a suspect, at a crime scene or abandoned, forensics experts test fire it, and those casings get entered into NIBIN, as well.

"It's revolutionary," said ATF Firearms Division Chief Michael Eberhardt. "Having that kind of information is remarkable for an investigator."

But for years, law enforcement wasn't using the technology to its full potential, Eberhardt said. Now, leads from smaller cases, where witnesses might be more likely to talk, can help solve the bigger cases.

"There has been some misunderstanding about how it's best utilized," said Eberhardt. "We're starting to now, nationally, see everybody understand what a powerful tool this is."

The ATF's <a href="https://www.atf.gov/firearms/national-integrated-ballistic-information-network-nibin" target="_blank" rel="noopener noreferrer">National Integrated Ballistic Information Network</a> is able to compare shell casings to link them to guns and crimes. ATF IBIS Chief Walter Dandridge shows how it works.

The ATF wants to shift how all law enforcement agencies use NIBIN — as a proactive crime-fighting tool in addition to the old reactive use in securing convictions once a suspect is caught. Eberhardt said comprehensive collection is the first step, since the more casings entered increase the likelihood of linking crimes together.

Newsham said it was essential in catching one of the suspects accused of gunning down Jamahri Sydnor, a bright, bubbly teenager who was caught in the crossfire while stopped at an intersection in Northeast.

"That was like losing a family member for all of us," said Newsham. Sydnor was the daughter of a veteran MPD detective.

"To be able to close that case over this technology, I mean, it makes you understand how the victims' families feel," said Newsham. "We had casings on all the scenes and so we were able to do a comparison."

Court records show how detectives used NIBIN to tie suspect James Mayfield to two other D.C. murders — one on the morning of his arrest. He's pleaded not guilty to all charges.

"Every time we help solve a case, what that means is we're getting a shooter off the street. So maybe the next victim doesn't exist," said ATF Special Agent Christie Weidner.

Weidner runs D.C.'s Crime Gun Intelligence Center — a partnership with D.C. police and Prince George's County police. Detectives work side by side at the center. Each agency has its own NIBIN machines and can get immediate results.

"The crossover between guns, the crossover between the individuals is very high," said Weidner.

Prince George's County police and Montgomery County police also practice comprehensive collection and enter every casing into NIBIN.

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But when the News4 I-Team surveyed departments across Northern Virginia, we found some aren't using the system as well — or at all. Some police agencies only require officers to enter casings found in high-crime areas and only test fire guns believed to have been used in a crime.

"We definitely see lower submissions from the Northern Virginia agencies than we do from some other areas," said Linda Jackson, director of Virginia's Department of Forensic Science.

Her labs are home to most of Virginia's NIBIN machines. It's been steadily reducing its firearms backlog, but still takes about four months to get results back to a detective.

Weidner told the I-Team she would love to bring Virginia on board as a partner in the Crime Gun Intelligence Center.

"That's something that's very high on our list of priorities to do, because not only do the criminals go between D.C. and Maryland, but they also come into Virginia," said Weidner.

Plus, federal data shows, of the guns recovered in the District, more come from Virginia than any other state.

But until March 2018, the Virginia labs only compared their NIBIN casings to others they had entered. Since they included D.C. and Maryland in their searches, roughly 48.5 percent of the hits at the Northern Virginia lab matched to outside agencies.

Jackson acknowledged it's possible the agency might have missed out on some potential NIBIN matches prior to the policy change.

She says the Virginia labs are increasing equipment and staff to produce leads faster, but the push to have every police department submit every casing could also have a downside.

"If all agencies did start doing that we would be overwhelmed very quickly," said Jackson.

That's just one of the reasons the ATF is now deploying 22 new NIBIN machines around the country.

"We are investing a ton of resources into making sure that we make it available to all our state and local counterparts," said Eberhardt.

One machine was initially slated for Northern Virginia, but ATF ended up sending it to Richmond instead, since Richmond had a much higher caseload and greater need.

Eberhardt says the ATF also has a fleet of mobile NIBIN vans that can travel when departments need help entering and matching casings. He says the federal agency will also try to push local departments that aren't collecting and entering every casing to see the value.

"The technology is still ahead of those departments," said Eberhardt. "As great as it is, it isn't the only responsibility that these local departments and these local laboratories have."

With a 38 percent spike in murders in the District in 2018, Chief Newsham said he'll take all the help neighboring police departments can give.

Newsham said utilizing comprehensive collection has required a shift in officer mindset over the past few years. But the more officers see a NIBIN lead pay off, the less convincing they require to get the evidence collected and write a report, even when no real crime has been committed.

"You never know if that shell casing is going to be the shell casing that closes one of your violent crimes," said Newsham.

Reported by Jodie Fleischer, produced by Rick Yarborough, and shot and edited by Jeff Piper.