AP National Writer
The beam from the intruder's flashlight pierced the blackness of the bedroom at 4:45 a.m., sweeping across the down comforter and into Eric Martin's eyes. Outside, the streets of his Utah subdivision lay still and silent.
But as Martin rolled to the floor, reached into the nightstand drawer and drew out his 9 mm pistol, the 46-year-old executive's mind raced with calculation: Would this man harm Martin's fiancee or her son? Was an accomplice outside waiting? What if he pulled the trigger and hit the sleeping 8-year-old across the hall?
In the weeks since the Connecticut school massacre, some of the most intense debate has swirled around how to keep guns from criminals without infringing on the ability of lawful gun owners, like Martin, to protect themselves and their families.
Indeed, protection is now the top reason gun owners cite for having a firearm, a new survey shows, a figure that has nearly doubled since 1999.
But even after years of study, there is little clarity on how, exactly, Americans use guns to protect themselves in moments of jeopardy -- or how often. Researchers known for sharp disagreement on the self-defense riddle say the answers may be shifting dramatically because of a steep drop in crime, an increase in guns and state laws giving owners more leeway to wield them.
Determining the absolute value of guns for self-defense is clouded by that complex dynamic of policy, judgment and circumstance. Still, both advocates of gun rights and of gun control understand the issue's importance in shaping the debate.
"When there's a threat outside your door, the police aren't going to be there ... the guys trained to save lives aren't going to be there," said Dom Raso, a commentator for the National Rifle Association's online news channel, in a video posted recently by the gun rights group.
And even while calling for new gun laws, President Barack Obama, too, acknowledged the legitimacy of self-defense in an April 8 speech in Hartford, Conn., when he recounted a conversation with his wife, Michelle, after campaigning in rural Iowa.
"Sometimes it would be miles between farms, let alone towns," Obama said. "And she said, 'You know, coming back, I can understand why somebody would want a gun for protection. If somebody drove up into the driveway and, Barack, you weren't home, the sheriff lived miles away, I might want that security.'"
With Americans split over whether guns more often save lives or jeopardize them, researchers have long parsed surveys of crime victims done in the 1990s, arguing over what the numbers mean.
But since then, crime has plummeted in the U.S. The rate of violent crimes including murder and assault fell by nearly half from 1992 to 2011, while the rate of reported property crime dropped 41 percent, data compiled by the Federal Bureau of Investigation show.
That drop has researchers considering the possibility, even the likelihood, that many fewer Americans are drawing firearms to protect themselves.
"I'm pretty confident that whatever the number is, it did go down ... because overall crime went down," said Gary Kleck, a Florida State University criminologist whose 1990s research, widely cited by gun rights activists, concluded that Americans drew their firearms in self-defense up to 2.5 million times a year. That translates to about 3 percent of all gun owners during the course of a single year.
But the drop in crime means there are far fewer occasions now for Americans to use guns for self-protection, Kleck said, making it likely that the number of annual self-defense usages of guns "should be about half as big now as they were back then, 20 years ago."
Even if such a drop were documented, it would still leave a scenario of relatively widespread use of guns for self-defense suggested by Kleck far at odds with research done by his critics.
The most outspoken has long been David Hemenway, director of the Harvard University Injury Control Research Center. He contends Kleck's survey vastly overinflates the number of times people use guns to defend themselves -- for example, by estimating thousands during the course of break-ins, though many of those homeowners either didn't own guns or remained asleep during the crime. Kleck, in turn, says Hemenway and others depend on surveys that significantly undercount self-defense gun use.
Hemenway, also relying on 1990s surveys, concluded Americans were then wielding guns for self-defense about 200,000 times annually.
Others researchers, analyzing the federal government's National Crime Victimization Survey, say the number of times guns were drawn for self-defense was even lower, about 80,000 times a year.