ON BORDER VIOLENCE, TRUTH PALES COMPARED TO IDEAS

When Representative Gabrielle Giffords, Democrat of Arizona,
announced that the Obama administration would send as many as 1,200
additional National Guard troops to bolster security at the Mexican
border, she held up a photograph of Robert Krentz, a mild-mannered
rancher who was shot to death this year on his vast property. The
authorities suspected that the culprit was linked to smuggling.

"Robert Krentz really is the face behind the violence at the
U.S.-Mexico border," Ms. Giffords said.

It is a connection that those who support stronger enforcement of
immigration laws and tighter borders often make: rising crime at the
border necessitates tougher enforcement.

But the rate of violent crime at the border, and indeed across
Arizona, has been declining, according to the Federal Bureau of
Investigation, as has illegal immigration, according to the Border
Patrol. While thousands have been killed in Mexico's drug wars,
raising anxiety that the violence will spread to the United States,
F.B.I. statistics show that Arizona is relatively safe.

That Mr. Krentz's death nevertheless churned the emotionally charged
immigration debate points to a fundamental truth: perception often
trumps reality, sometimes affecting laws and society in the process.

Judith Gans, who studies immigration at the Udall Center for Studies
in Public Policy at the University of Arizona, said that what social
psychologists call self-serving perception bias seemed to be at play.
Both sides in the immigration debate accept information that confirms
their biases, she said, and discard, ignore or rationalize
information that does not. There is no better example than the role
of crime in Arizona's tumultuous immigration debate.

"If an illegal immigrant commits a crime, this confirms our view that
illegal immigrants are criminals," Ms. Gans said. "If an illegal
immigrant doesn't commit a crime, either they just didn't get caught
or it's a fluke of the situation."

Ms. Gans noted that sponsors of Arizona's controversial immigration
enforcement law have made careers of promising to rid the state of
illegal immigrants through tough legislation.

"Their repeated characterization of illegal immigrants as criminals -
easy to do since they broke immigration laws - makes it easy for
people to ignore statistics," she said.

Moreover, crime statistics, however rosy, are abstract. It takes only
one well-publicized crime, like Mr. Krentz's shooting, to drive up fear.

It is also an election year, and crime and illegal immigration - and
especially forging a link between the two - remain a potent boost for
any campaign. Gov. Jan Brewer's popularity, once in question over
promoting a sales tax increase, surged after signing the immigration
bill, which is known as SB 1070 but officially called the Support Our
Law Enforcement and Safe Neighborhoods Act.

No matter that manpower and technology are at unprecedented levels at
the border, it may never be secure enough in Arizona's hothouse
political climate when Congressional seats, the governor's office and
other positions are at stake in the Aug. 24 primaries.

It took the Obama administration a few weeks to bow to that political
reality and go from trumpeting the border as more secure than it had
ever been to ordering National Guard troops to take up position there
- - most of them in Arizona, Mr. Obama assured Ms. Brewer in a private
meeting - because it was not secure enough.

Crime figures, in fact, present a more mixed picture, with the likes
of Russell Pearce, the Republican state senator behind the
immigration enforcement law, playing up the darkest side while
immigrant advocacy groups like Coalicion de Derechos Humanos (Human
Rights Coalition), based in Tucson, circulate news reports and
studies showing that crime is not as bad as it may seem.

For instance, statistics show that even as Arizona's population
swelled, buoyed in part by illegal immigrants funneling across the
border, violent crime rates declined, to 447 incidents per 100,000
residents in 2008, the most recent year for which comprehensive data
is available from the F.B.I. In 2000, the rate was 532 incidents per 100,000.

Nationally, the crime rate declined to 455 incidents per 100,000
people, from 507 in 2000.

But the rate for property crime, the kind that people may experience
most often, increased in the state, to 4,082 per 100,000 residents in
2008 from 3,682 in 2000. Preliminary data for 2009 suggests that this
rate may also be falling in the state's biggest cities.

What is harder to pin down is how much of the crime was committed by
illegal immigrants.

Phoenix's police chief, Jack Harris, who opposes the new law, said
that about 13 percent of his department's arrests are illegal
immigrants, a number close to the estimated percentage of illegal
immigrants in the local population. But the Maricopa County Sheriff's
Office, which runs the jail for Phoenix and surrounding cities and is
headed by Joe Arpaio, a fervent supporter of the law, has said that
19 percent of its inmates are illegal immigrants.

Scott Decker, a criminologist at Arizona State University, said a
battery of studies have suggested that illegal immigrants commit
fewer crimes, in part because they tend to come from interior cities
and villages in their home country with low crime rates and generally
try to keep out of trouble to not risk being sent home.

But he understood why people's perceptions of crime might lag behind
what the statistics show. "Hard as it is to change the crime rate, it
may be more difficult to change public perceptions about the crime
rate, particularly when those perceptions are linked to public
events," Mr. Decker said.

He added, "There is nothing more powerful than a story about a
gruesome murder or assault that leads in the local news and drives
public opinion that it is not safe anywhere."

Kris Kobach, a University of Missouri law professor who helped write
the Arizona immigration law, pointed to crimes like a wave of
kidnappings related to the drug and human smuggling business in
Phoenix, something Ms. Brewer herself noted when she signed the law.

Although the reports have dipped in the past couple of years, the
police responded to 315 such cases last year.

"That's scary to people, and people react to that all over the
state," Mr. Kobach said. "They are concerned. 'That might happen in
my part of the city eventually.' "

Terry Goddard, the state attorney general, who does not support the
immigration law, said the drop in violent crime rates might not
reflect the continued violence, often unreported, that is associated
with smuggling organizations.

Mr. Goddard said he doubted that the immigration law would put a dent
in the smuggling-related crime that grabs attention in the state. For
that reason, Mr. Goddard, who is running to be the Democratic nominee
for governor in the primary, said he backed the deployment of
National Guard troops and supports increasing manpower and spending
on police and prosecutor anti-smuggling units.

Brian L. Livingston, executive director of the Arizona Police
Association, said he would prefer more attention on the border, too.
But until then, he said, laws like Arizona's are necessary.

"We know the majority of people crossing across are not criminal, but
unfortunately some criminal elements are embedded with them," he
said, adding, "Governor Brewer gets that."

As Ms. Brewer put it just after signing the bill: "We cannot
sacrifice our safety to the murderous greed of drug cartels. We
cannot stand idly by as drop houses, kidnappings and violence
compromise our quality of life."