Fake driver's licenses have long been considered the holy grail of underage youth — many have been brazenly handed over to liquor store cashiers in the quest for alcohol.

While that practice persists despite crackdowns, fraudulent IDs can signify much more than adolescent scheming in today's post-9/11 world.

That's where Martin Johnson, an expert in all types of counterfeiting, steps in.

The retired Howard County police officer volunteers his time, training county Police Department recruits to recognize "the tens of thousands of fraudulent identity documents that are out there," he said. He also teaches them how to spot counterfeit money.

The Ellicott City resident teaches simple ways to detect a bogus Social Security card or a fake $100 bill in a matter of seconds. And he can explain why the appearance of counterfeit money and IDs in a community can signal something worse — even the presence of terrorists operating somewhere in the vicinity.

Johnson is also a certified instructor with the U.S. Department of Homeland Security, and designs and presents training courses in the detection and prevention of domestic terrorism across the country for its Academy of Counter-Terrorist Education.

"We have, most recently, been seeing counterfeit $100 bills of a very high quality," he said, emphasizing that it's not just a local phenomenon.

A surveillance video shot at an Ellicott City restaurant recently showed the same person pulling a $100 bill from a stack in his pocket to make a small purchase two weeks in a row.

"This is how counterfeiters turn their fake bills into real money," he explained. "When it worked the first time, the guy returned for more."

The current crop of high-quality bills passes such acceptable detection methods as the "counterfeit detection pen," he said. A mark is made on the bill with special ink that supposedly only changes color when it reacts to the specific cellulose fibers in authentic paper currency.

But Johnson isn't sold on the low-tech device, which can be purchased for $3 at office-supply stores.

"The pen is easily fooled and only catches a fraction of the counterfeit bills" in circulation, he said. He estimates that nearly half of county businesses use them.

"Some clever counterfeiters even preprint a phony mark on their bills," he said, and this convinces some business owners that the money was already checked with a pen by a previous merchant — and must therefore be legal tender.

That's why Johnson is pleased that a redesigned $100 note, which is easier to authenticate and harder to replicate, was issued Oct. 8 by the Federal Reserve.

The bills have two new security features: a blue 3-D security ribbon and a color-changing Liberty Bell in an inkwell. Details on all of the security measures and an interactive bank note that demonstrates the latest enhancements are available online at NewMoney.gov, he said.

Yet counterfeiters aren't the perfectionists we might assume them to be, Johnson says.

He makes his case by placing an array of confiscated fake IDs on a table, some with glaring, amateur-level mistakes. There's a grossly oversized Social Security card and a driver's license with a young man's photo issued in the name "Kelly Marie."

He also displays two examples of so-called international driver's licenses (which don't exist anywhere in the world), as well as convincing replicas of all denominations of U.S. currency, some better than others.

"Most criminals are not considering the odds of getting caught — they live in the moment," he said. "Think about it: A fraudulent document only has to be good enough to be accepted and get the job done — nothing more."

The county's overall success at uncovering fake money and IDs, outside of police work, lies in the hands of business owners and the steps they take — or don't take — to thwart counterfeiters, he notes. They are asked to notify police when they come across something suspicious and police confiscate the money or ID for further investigation.