The politicians of Arizona decided that Jared Lee Loughner was a decent law-abiding citizen. As such, they determined that he deserved to be able to legally purchase virtually any type of firearm he desired and to legally carry that firearm in a wide variety of public and private spaces.

So Loughner legally bought a gun designed to kill many people extremely rapidly and he carried the gun legally. He was carrying his gun early Jan. 8 when he was stopped by police.

It was only after he started shooting at innocent people that he stopped being a decent law-abiding citizen.

In all other high-income democracies, it would have been very difficult for Loughner legally to have obtained his weapon. Some of these countries have very few private guns (e.g., Japan, United Kingdom), while others have fairly many (e.g., Canada, Australia, Israel, Switzerland, Finland), but have more restrictive gun laws than the United States.

Every one of these countries has been more successful than we have at keeping guns out of the wrong hands.

In Canada, for example, to legally buy a handgun requires a license, training, proof of legitimate purpose, a four-week waiting period, and two references, who must sign the application. Handgun ammunition magazines are restricted to 10 rounds or less.

I have been studying injury and violence prevention for more than 40 years. What is known is that all injuries follow generally predictable patterns, and most are preventable.

While we cannot predict at the individual level which specific people will be shot, we can predict fairly accurately at the population level about how many people will be shot.

Thus I can predict with complete confidence that in the next decade, the United States will have many more homicides than the other high-income democracies, and many more mass shootings.

As a benchmark, in 2003, the United States homicide rate was seven times higher than that of these countries, largely because our firearm homicide rate was 20 times higher.

Why do these other countries have such low homicide rates?

Their children watch the same violent movies and play the same violent video games as our children. They have as much bullying in schools. They have oppressed minorities, and similar rates of non-firearm crime and violence (assaults, robbery, burglary, rape). And they all have crazy people.

But these other countries have stricter gun policies than the United States. And when disaster happens, they typically respond.

Following the 1996 Port Arthur, Tasmania, massacre of 35 people, Australia acted quickly to effectively ban assault weapons. A mandatory buyback obtained more than 650,000 of these guns from existing owners. Australia also tightened requirements for licensing, registration and safe gun storage of firearms.

The result? In the 18 years before the intervention, Australia had 13 mass shootings. In the dozen years since, there has not been a single one. The laws also helped reduce firearm suicide and non-mass shooting firearm homicide.

Like the citizens of these other high-income countries, we are fortunate to live in a democracy. We can decide our own fate.

I weep for the innocent victims in the Tucson shooting, and for the many who will be killed in the future if we continue to define the Loughners of the world as decent law-abiding citizens and give them immediate access to the most lethal of firearms - until they prove us wrong.

David Hemenway, Ph.D. Professor of Health Policy Director, Harvard Injury Control Research Center Harvard School of Public Health 677 Huntington Ave. Boston, MA 02115 (617) 432-4493