Do guns make people safer or more susceptible to violence? Does banning assault-style weapons or expanding background checks save lives, or are such measures merely inconveniences for law-abiding gun owners?

These are just some of the questions in the debate over gun control, with advocates and foes lobbing a dizzying number of statistics and studies to make their case. Often, those facts and figures contradict one another.

The lack of objective research on gun violence has become evident as Minnesota and the nation grapple with a slew of proposed changes to gun laws after the Newtown, Conn., school shooting that killed 26. And some say it’s time to reinvest in research, which was virtually cut off more than 15 years ago after opposition from pro-gun lobbyists.

“We can make a big difference on this issue if we stop posturing and blocking good, objective research,” said Arthur Kellermann, a clinician and researcher who has practiced and taught emergency medicine for more than 25 years.

RESEARCH DRIES UP

Federal funding for research on preventing gun violence has been seemingly nonexistent since 1996. That’s after public health research on guns started to take off and get noticed by the public.

Kellermann is the co-author of one of the best-known gun studies, published in the New England Journal of Medicine in 1993. He found that when people had a gun in the home, they were more likely to harm someone they knew than to protect themselves.

For every time a gun in the home was used in a self-defense or legally justifiable shooting, there were four unintentional shootings, seven criminal assaults or homicides, and 11 suicides or suicide attempts, Kellermann found.

“The odds of a tragedy, whether it be suicide, murder or accidental death by gun, are substantially greater than the gun protecting them or their family,” said Kellermann, who is now in policy analysis at the Rand Corp.

His research was funded by the Centers for Disease Control and Prevention. But the study, and others funded by the CDC’s injury center, angered the National Rifle Association and other gun-rights supporters. Congress stripped funding from the CDC and added this disclaimer in its appropriation bill:

“None of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control.” While that never specifically blocked research into gun violence, the language was broad enough to scare CDC officials off, researchers say.

But NRA lobbyist Chris Rager said it was only meant to stop politically slanted publicly funded research.

“It in no way means gun violence can’t be studied,” Rager said. “We just don’t want propaganda to be funded with taxpayer dollars.”

Kellermann has been dubbed anti-gun, a label he disputes. The native Tennessean grew up with guns and owned guns. But since the CDC funding dried up, there is only a fraction of the money that existed for objective research of the effects of guns on public health. That makes it impossible to achieve the kind of results against gun violence that public health officials have achieved against car accidents, drownings and and deaths from fires, all without banning cars or swimming pools, Kellermann said.

“There’s plenty of good data and research out there,” Kellermann said. “The problem is it’s 15 to 20 years old.”

SO WHAT DO WE KNOW?

So what does that mean for the gun-control debate? Even more cherry-picking of data and surveys by advocates and foes.

That includes Minnesota, where lawmakers have listened to dozens of hours of testimony on proposed changes to gun laws. Here are a few of the recurring claims:

— There are more guns than ever in the U.S., but gun violence has gone down.

This claim by gun-rights supporters is mostly true.

It’s hard to get an accurate count of how many guns are in the country, but by most accounts there are more than ever at around 300 million. And gun murders are at their lowest rate in the U.S. since the CDC started tracking them in 1981. There were 11,078 murders with guns in 2010, or about 3.59 per 100,000 people.

Aggravated assaults and robberies using guns are also on the decline, at 138,336 and 122,300 respectively in 2011, according to the Justice Department.

But nonfatal gun injuries from assaults have increased for the past three years. And suicides by gun are also on the rise, at a high point since 1998.

— Most Americans — including gun owners — support more stringent background checks.

That is mostly true.

Gun-rights groups such as the NRA have argued that some of those surveys are skewed because they are being commissioned by gun-control advocates.

But several reputable, nonpartisan organizations, including the Johns Hopkins University Bloomberg School of Public Health and the Pew Research Center, found that in general, gun owners favor background checks. Pew on Feb. 13 released a poll showing that more than 80 percent of gun owners favor making private gun sales and sales at gun shows subject to background checks and more than 60 percent support the creation of a federal government database to track all gun sales. (The poll had a margin of error of plus or minus 2.9 percentage points.)

“Clearly, the polls have shown the strong, strong support for strengthening legislation for handgun purchases,” said Dennis Flaherty, executive director of the Minnesota Police and Peace Officers Association. “We think there are just too many transactions that take place every day, on the Internet, over the backyard fences, out of the trunks of cars, what we call private sales, that are being conducted that require no background investigation whatsoever.”

The NRA opposes universal background checks, arguing they will never be truly “universal” because criminals will not submit to the system. The organization cites its own survey of NRA members, in which 92 percent opposed such a proposal.

But not all gun owners are NRA members. And as with any poll, the devil is in the details and the wording of the questions.

When the NRA polled members on background checks, those surveyed were asked if they favored or opposed “a new federal law banning the sale of firearms between private citizens.”

Groups advocating for gun control, like Mayors Against Illegal Drugs, do the same thing. In a poll last year commissioned by the group, the background-check question focused on anyone “purchasing a gun.” Gun-rights supporters say that doesn’t include inheriting guns from family members or friends, which doesn’t require a background check but would under many of the proposed laws.

— Do background checks work?

It depends on the definition of “work.”

Gun-rights supporters say criminals won’t submit to background checks because they know they won’t pass, so more regulations won’t stop gun violence and will only punish law-abiding gun owners

But law enforcement and public health advocates say that while background checks won’t eradicate gun violence, they do help keep guns out of criminals’ hands.

A 2013 study published in the journal Injury Prevention surveyed prison inmates in the 13 states with the weakest gun laws to see where they got their guns and whether they would have been prevented from getting them if laws were stricter.

The Johns Hopkins Bloomberg School of Public Health researchers found that nearly three of every 10 gun offenders would have been prohibited from purchasing or possessing a firearm when they committed their most recent offense if their states had more restrictive laws in place.

However, stricter gun laws would not have prevented the majority of gun crimes, the study found. About 34 percent of the inmates got their guns from family or friends and another 30 percent got them from drug dealers or other black-market sources.

“We are uncertain about the degree to which stricter legal standards for firearm possession might deter criminal gun possession and use,” the researchers wrote. “But, adding barriers for the acquisition of guns by high-risk persons is an underused potential intervention.”

That’s exactly the problem for gun owners who follow the rules, said Andrew Rothman, vice president of the Minnesota Gun Owners Civil Rights Alliance.

“No background check is going to stop a criminal from getting a gun,” Rothman said. “I know that. And Minnesota gun owners know it.”

But there is research that shows background checks have helped reduce the number of criminals who get guns, said Jennie Green, an associate law professor at the University of Minnesota. And while gun-control advocates admit more stringent checks won’t stop all violent crime, they argue that they will save lives.

A 1999 study published in the American Journal of Public Health compared people who had felony arrests but no convictions who were able to purchase handguns after a background check with convicted felons who were denied handgun purchases. Those who were able to purchase a gun were more likely than those denied guns to have subsequent arrests involving a gun or violence.

David Chipman, a retired agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives who works for the gun-control group Mayors Against Illegal Guns, said requiring background checks does reduce violent crime.

“The fact that this state and that this government continues to allow the sale of any gun without a background check is not only reckless, not only irresponsible, it is downright dangerous,” Chipman said. “Will criminals attempt to thwart this regulation? Of course. That’s what criminals do. But as criminals and the severely mentally ill make these attempts, their efforts will necessarily become more complex, mistakes will be made, and law enforcement will be there.”

LOOKING FOR DIALOGUE

The problem with some of the more recent studies is that they are being funded by private foundations that want skewed research to promote a particular point of view, Kellermann said.

“They’re not interested in objective research,” Kellermann said. “They are pushing a political agenda.”

But researchers say they have a glimmer of hope. One of 23 executive actions President Barack Obama took on gun violence in January was to lift the virtual ban on research into the public health effects of gun violence. But even though the CDC is free to work on that issue again, Congress ultimately approves its funding.

Green said she is heartened by the decision, hoping policymakers can have a more informed dialogue about gun violence.

“Numbers can mean something, but they have to be documented and studied,” Green said.

Kellermann pointed to an initiative in Atlanta that reduced violent crime. In the 1990s, police, prosecutors, health workers and researchers partnered to fight juvenile gun violence in the city’s hotspots. Kellermann was one of those researchers, from Emory University.

During the first several years, the number of homicides dropped but mirrored declines statewide and across the nation.

But gun crimes continued to decline, by 44 percent alone from 2002 to 2005. Violent crime overall fell by 37 percent.

“That was done without passing one single gun-control measure,” Kellermann said. “That’s why I hope when people stop yelling at each other we can have good information and make informed decisions that curb gun violence without infringing on people’s Second Amendment rights.”

Megan Boldt can be reached at 651-228-5495. Follow her at twitter.com/meganboldt and facebook.com/PioneerPressPolitics.