Fairfax County’s Police Department has been around for more than 70 years, but its Criminal Intelligence Division (CID) wasn’t created until after the 9/11 tragedy.

“Five detectives and one supervisor were in a lunchroom in the Massey Building when we first discussed it,” said CID Det. Doug Comfort. “There was a phone on the wall and we had to leave the room between noon and 1 p.m. so others could eat lunch.”

Comfort’s in his 39th year in law enforcement; he retired as a detective sergeant after 24 years with the Vienna Police Department and has been with the county police for 15 years. And he was addressing a recent meeting of the Sully District Police Station’s Citizens Advisory Committee.

“We hadn’t worked in international terrorism before 9/11,” he said. “But we worked on the 9/11 bombings with the Pentagon and New York because nine of the bombers lived here in Fairfax County — and that concerned us.”

Then, some 18 months ago, Comfort and an Arlington police captain wrote a course on tactical community policing for homeland security. “In the community, if you lose control, fear rises,” said Comfort. “So we have to teach you what we want you to see, how to collect information and who to give it to.”

Nowadays, he said, “Cell phones can be people’s notepads; you can leave messages in them about things you see that may not be right.” He also stressed that police target behavior, not a particular person.

“We need four things in every terrorist case — names, vehicles or license-tag information, locations and phone numbers,” said Comfort. “Make a note of people acting suspicious or things that make you uncomfortable — something that doesn’t seem to fit.”

He encouraged residents to be wary, for example, of people asking how things are done or asking for too much specific information, above the normal level of curiosity. He said they should be concerned about people who challenge others or ask them to do something they wouldn’t normally do.

“Be suspicious of people asking for your personal data,” said Comfort. “Or people wanting to photograph certain things, such as access points to buildings, a company’s personnel or people doing their jobs.”

In the CID, he said, “We watch people and do surveillance. Do they switch cars or meet with another person? We notice people using binoculars, taking notes and measuring distances. And we’re suspicious of people meeting in a restaurant, but only having water, talking and then leaving by different entrances than they came in, originally.”

People buying unusual items or large amounts of them are also cause for concern. “For example, if I had 18,000 pounds of fertilizer delivered to a house, that would be suspicious,” said Comfort. “I’d have to have an awful big lawn — and mow it four times a day.”

Since people can die by biological, nuclear, incendiary, chemical and explosive means, he said, “We want to know about people with weapons, ammunition and powders, as well as people misrepresenting themselves.” And, he added, authorities are always concerned about potential sabotage or vandalism to critical infrastructure, such as a water-treatment plant.

“So if you see a hole in a fence by something important, we want to know about it,” said Comfort. “We’d rather you’d call us — even if your tip doesn’t pan out — because it may be the piece of a larger puzzle we’re working on.”

However, he stressed, “If you do see something, don’t put yourself in danger. Take a deep breath and don’t get excited. That way, you’ll be able to remember more information.”

Overall, Comfort urged residents to “record, remember and report.” They may contact police at the non-emergency number of 703-691-2131; or if they have a bona-fide emergency, they may call 911.

“If you think it’s suspicious, we think it’s suspicious,” he said. “And it’s something you have to train yourself to do — not just to see things, but to really study things. And when gathering information about a person, don’t look for someone’s height and weight as much as identifying characteristics. What would separate him from everybody else?”

“We do this for you, and we ask you to help us do it,” continued Comfort. “This is for your quality of life.”