LAS VEGAS, Nev. — Divorce lawyers have a friend in Facebook.

It’s a fishing expedition — in a stocked pond. Delving into the social networking website "is fun for lawyers because you can find the proverbial smoking gun," says Mary Anne Decaria of Reno, president of the Nevada chapter of the American Academy of Matrimonial Lawyers.

One recent example: A Las Vegas attorney helped a professional basketball player lower his monthly child support payments to his ex-wife, thanks in part to a photo of the woman’s mother on Facebook.

Attorney Marshal Willick set out to prove that the ex-wife had been spending only a few hundred dollars on the basketballer’s child even though he was giving her a monthly check of more than $10,000. Willick struck gold when the mother’s Facebook page showed her standing next to an expensive new Jaguar automobile. It turned out the ex-wife had used money from her child support checks to buy the car for her mother.

Welcome to 21st century family law, a branch of litigation that over the past five years has become increasingly reliant on Facebook, MySpace, Twitter and other popular social networking websites.

Members volunteer information that can shoot holes through such court contentions as "I’m a responsible parent. Therefore, I deserve custody of the child," or "I’m broke and can’t afford alimony."

A survey released in February by the American Academy of Matrimonial Lawyers confirmed the increasing reliance on Internet-based social networking evidence in divorce cases and cited Facebook as by far the leading source of that information.

According to Facebook’s numbers, it has about 120 million users in the U.S. Estimates are that slightly more than a million Nevadans are Facebook users who share personal information with friends, relatives and co-workers. Those who aren’t careful about its privacy settings often learn to their chagrin that revelations they thought would be kept among a small group of people actually can be broadcast to a far wider audience.

And no matter the privacy settings, when a court battle gets under way, lawyers can be counted upon to pursue records for Facebook and other social media.

Las Vegas attorney Edward Kainen, an academy member, has taken advantage of social networking information on numerous occasions.

"It’s fairly common when you deal with child custody cases," Kainen says. People post all sorts of things that lawyers can use against them.

Particularly common are photos of a drunk parent, not exactly the image you would want a judge to see while trying to plead your case in a custody or alimony dispute.

In one case where a man in a divorce case claimed to have no money to pay alimony, Kainen obtained Facebook photos showing the guy in a drunken stupor inside a Las Vegas resort.

"He claimed he was only earning $1,300 a year, but he was partying much like a rock star," Kainen says. The case was resolved in favor of Kainen’s client.

In another case, a parent who had custody of a teenager claimed to be properly supervising that child. But Kainen won the case for the other parent partly on the strength of information from a MySpace page in which the teenager bragged about being sexually active.

Willick says the wealth of social networking information that can be gleaned from the Internet has made it indispensable in gathering evidence. He even uses websites such as the popular Wayback Machine to retrieve older, incriminating Internet submissions that an opposing spouse assumed had been removed from cyberspace.

"It’s amazing what people tell the universe," he said. "It’s unwise to put something on the Internet and say something else in court."

Willick this year won an alimony modification dispute for a woman whose unemployed ex-husband had earned a six-figure salary as an information technology professional. The man, who wanted his alimony payments reduced, had told a judge that he was diligently looking for work in his profession but was unable to find a job. Willick shot holes through that story when he produced the man’s Facebook page on which he claimed he was a helicopter pilot.

Willick was able to successfully argue that the man "clearly wasn’t seeking work in his field. If you’re putting out information that you’re a helicopter pilot, you’re not likely to get hired by an information technology company."