Fairfax County Police Chief David M. Rohrer. Not good at accepting compliments. (Cliff Owen/AP)

When Fairfax adopted new computer technology last year to track all of its records, it also adopted “incident-based reporting” of crime, which counts each crime that occurs during a single incident. The previous system counted only the most serious crime in that incident. So if you were shot AND robbed AND had your car stolen, that only counted as an aggravated assault. (And a really bad day.) Now it counts as all three.

So that should mean higher crime numbers, yes? In some areas, yes. For the most part, no. Overall, even under the new system, there were 18,938 crimes logged in Fairfax in 2009; last year, 17,453. Comparing apples and oranges? Maybe. But in a growing county of a million people, where your new system should count more crimes, the numbers STILL went down. That’s impressive.

Now, the increase that scares Fairfax police the most was aggravated assault. In 2009, there were 309. But under the new incident-based reporting system, there were 450. That’s a 45.6 percent increase, or a possible indication of anarchy in the streets. But Fairfax went back through the 2009 reports and found that if you counted them under the new system, it would have been 440, not 309. An increase of 2.2 percent. Anarchy quelled. Robberies were also up slightly.

Murder and rape, you can’t really fudge those numbers. Murder, up 2, from 14 to 16. Rape, down 29 percent, from 105 to 74. Those stats, in the suburbs, often aren’t large enough to indicate trends.

But burglaries, however you count ‘em, declined to another all-time Fairfax low, 1,211 from 1,385 in 2009. Motor vehicle thefts also dropped, from 1,096 to 963. Larcenies, which make up the bulk of raw crime stats, dropped from 15,643 to 14,345, Those are the quality of life indicators in places like Fairfax, and they’re all going in the right direction. As of now.

But the Fairfax police, under Chief David M. Rohrer, have always been reluctant to take credit for any of this. So we’ll put this up on the ol’ Internet, and then let the chief have a look and post his response right here. Stay tuned.

I would also like to offer any criminals out there the opportunity to respond, and provide their analysis of why crime continues to drop in Fairfax. E-mail me directly at jackmant@washpost.com.

UPDATE, 5:15 p.m.: Chief Roher has checked in, as follows:

We don’t take all the credit when crime rates go down because then you’ll want to put all the blame on us when they go up! Just kidding, we take crime data very seriously, and we did not, after much discussion and even though the “story” looks good overall, feel it was fair or ethical to compare 2010 crime data to past years as we have transitioned to a new Records Management System (RMS) and are also now able to use a more comprehensive and meaningful incident-based crime data collection and reporting system (known as NIBRS) compared to the traditional UCR summary report system.

The reality too is that crime rates are complex and are affected, positively and negatively, by many disparate factors. Some of those are within the control of a police department, such as the deployment of specific resources, but some not, such as demographic shifts and budgets. I also worry, as I’m paid to do, about what I don’t know. Some crime (too much in some categories such as domestic violence) goes unreported - and we cannot lose sight of that. No one deserves to be a victim of a crime, particularly a violent one, and we want all crimes reported so we can investigate those and, hopefully, identify and arrest offenders before they prey on others. More reports and data also help us better identify any trends or patterns of concern.

I also never focus on a specific up or down statistic, I look for trends, whether on a micro or macro level, so that we can better understand the root cause, and then focus our resources and problem-solving strategies to make a difference. Obviously, the crime rate in Fairfax County is comparatively low, and unlike some outside policing, I strongly believe that effective policing strategies work - police matter. I’m proud of the professionalism and dedication that our men and women, whether sworn, civilian, or volunteer, routinely demonstrate in protecting our community. They are the “boots on the ground.” It is truly a team effort, to include our patrol officers, detectives, civilian crime analysts, specialty units, commanders, and many more. They work hard and deserve the credit – not the chief.

But, the other reality is that we serve a community that cares, one that is made up of concerned elected officials, effective County leadership, quality schools, many County agencies, non-profits, businesses, and faith-based organizations that partner with us, effective Commonwealth’s Attorney’s Office and strong courts, excellent parks and recreation – they too all deserve credit.

And finally, and most importantly, our wonderfully diverse community is made up of engaged residents and neighborhoods – they care. They partner with us, they support us, and they help us prevent, combat, and reduce crime. They expect, and deserve, a safe community - they deserve credit. I thank our community - my community - whenever I can.

Colonel Dave Rohrer

Chief of Police

Fairfax County Police Department