Click photo to enlarge
An airline passenger undergoes a full body scan at O'Hare International Airport Wednesday, Nov. 17, 2010 in Chicago. (AP Photo/Charles Rex Arbogast)

As nearly 2 million holiday travelers pack Bay Area airports starting Friday, local prosecutors have a warning for overzealous security agents performing the new federal pat-down: touch passengers the wrong way, and we'll throw you in jail.

Unsuspecting families and rookie travelers using San Francisco, San Jose and Oakland international airports this Thanksgiving might not know about the Internet catchphrase "don't touch my junk" or the Transportation Security Administration's more invasive searches. But by the end of next week, they might know a little too much about them.

Although authorities in San Mateo and Santa Clara counties said they have not received any criminal complaints since the procedures began earlier this month, the searches can involve touching of the genital and breast areas, which critics say is akin to sexual assault.

The TSA says the pat-downs are rare and most commonly used when travelers opt not to go through the full-body X-ray scanners, which reveal what is underneath passengers' clothes and are used at all three Bay Area airports. Passengers who refuse both options would not be allowed to travel, and the TSA could fine them up to $11,000 if they cause delays for other passengers.

As the pat-downs make their prime-time debut during the Thanksgiving rush, the San Mateo and Santa Clara district attorneys offices said Wednesday that they would bring charges against TSA agents at SFO and San Jose airports, respectively, if they committed sexual crimes during searches. They said charges would be evaluated on a case-by-case basis and that prosecutors would take into account the fact that the agents were doing a job.

If they cross a line, that's sexual battery, said Steve Wagstaffe, San Mateo County's chief deputy district attorney.

Wagstaffe said it's no different from when prosecutors charge dentists, doctors or police officers who abuse their power by touching people in a sexual manner. He said the key to proving a criminal offense is the sexual intent behind the groping.

"TSA does not have any special immunity from everybody else," Wagstaffe said. "If an employee of TSA inappropriately touches the privates of another person, and they do so with a sexual or lewd intent, then that's either a misdemeanor (if it's over the clothing) or a felony crime (possible when touching the skin)."

The pat-down backlash swept the nation this week when a fed-up San Diego passenger posted to the Web a recording of his encounter with a TSA agent in which he told the worker he would have him arrested if he touched his "junk." Another online recording showed a 3-year-old being searched aggressively in Tennessee.

Both spoofs and legitimate complaints have swamped the Internet and talk shows since, and dozens of people posted on Twitter on Wednesday that they had either survived the "groping" at SFO or joked they were ready for it. Some who had already experienced the pat-down at SFO said they felt violated, while others said it was a good alternative to the X-ray machine.

"You must, unfortunately, be prepared for these screenings. There's no question you lose some dignity over what they're doing, and it's not a terribly pleasant experience," said Henry Harteveldt, a San Francisco-based aviation analyst with Forrester Research. He advised passengers to evoke their right to have a witness present during the search.

A TSA spokesman did not return calls for comment Wednesday, but the agency's administrator, John Pistole, told congressional leaders that he understood the privacy concerns but that government must provide the best possible security for air travelers.

Pistole acknowledged that the new procedures were more invasive but said they were necessary to detect potential terrorist threats.

About 1.88 million people will fly in and out of the Bay Area's three largest airports during the 11-day rush from Friday to Nov. 29, officials said. Most will be at SFO, which expects 1.23 million passengers, an increase of 4 percent from last year's Thanksgiving peak and a 9 percent rise over a typical 11-day stretch.

During the busiest days, there could be nearly 200,000 people at the three hubs, airport officials predicted.

Harteveldt and airport officials advised passengers to arrive early during the rush, typically 90 minutes ahead of departure time for domestic flights and two hours for international trips.

SFO spokesman Mike McCarron said peak security waits should be 15 minutes, and officials at San Jose and Oakland airports predicted it would not be any worse at their hubs.

Mike Rosenberg covers San Mateo, Burlingame, Belmont and transportation. Contact him at 650-348-4324.