Robert Wells advertised himself on an online dating service as a semiretired physician who enjoys wine tasting, "The Sopranos" and reading science fiction.

But a woman surfing the Web site recognized the Walnut Creek man from another dating site she'd used a year earlier. She told the current service, Dallas-based True.com, that Wells was lying. Not only had the medical board revoked his license, according to a lawsuit, but he also was a convicted sex offender.

"Before I went out with anyone, I always checked their backgrounds," said the Sonoma County woman, whose name is being withheld because she fears her safety is at risk.

The company sued Wells earlier this month in U.S. District Court in Texas, alleging Wells committed fraud by misrepresenting himself when he agreed, during sign-up, to a contract stating he was not a felon. Wells was one of what True.com officials say is less than 10 percent of people who get around the company's background check.

"I make a promise to my members," said Herb Vest, True's chief executive officer. "If you are clever enough to get around our site securities, I'm going to prosecute."

True.com is suing Wells for at least $200,000. The suit comes at a time when several state governments, including California's, are considering laws to ensure online dating services conduct background checks or tell visitors that the site does not conduct background checks -- a move that blocks revenue from potential members who get screened out.

Now some sites including Yahoo Personals, eHarmony and Match.com include a contract that asks members to state that they are not convicted felons.

Rather than background checks, Match.com staff members monitor communications between members to help make sure people don't post offensive photos and notes. The site also includes safety tips, and members can contact the staff if they perceive a problem.

Few online dating companies conduct background checks, leaving members to independently beware, said Parry Aflab, executive director of Wiredsafety.org.

Vest said his company conducts background checks about each person who signs up. The checks try to confirm that the potential member is unmarried and has no felony convictions. The weeding-out process causes Vest's company to lose about 10 percent of its business right off the top: about 5 percent of applicants are married and another 5 percent are felons.

"If you live in a place that doesn't have open criminal records, your criminal history might not show up," said Chris Hoofnagle, senior counsel with the Washington-based Electronic Privacy Information Center. "If you have a common name, you might show a criminal history that doesn't belong to you."

The 55-year-old Sonoma County woman who identified Wells first met him in 2004 on eHarmony.com. The woman thought the ophthalmologist was "creepy."

"In his profile, he talks about how he's a 'sensuous person.' That sends out bells," she said. "I kept writing because I wanted to see if there was something wrong with him. ... If my feeling was right, I wanted to make sure somebody like that wouldn't be online."

She corresponded with Wells until he revealed his last name. With that, she checked his background and learned he was convicted of "attempted lewd and lascivious act with a child under 14" in 2001 in Stanislaus County.

According to court documents, Wells had met a fictitious 13-year-old girl in a chat room during a sheriff's department sting operation. He served three years of county probation and lost his medical license.

"He would ask me questions about if I had fantasies of being abducted, kidnapped and raped," said sheriff's detective Ken Hedrick, who pretended to be the girl.

The Sonoma County woman contacted eHarmony, which removed Wells from the site, she said. She then saw him on Match.com and True.com in October. True sued him a month later.

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