The skycaps ordinarily spend their workdays lifting heavy baggage onto carts at Logan International Airport's curbside, but on this recent evening they raised wine glasses and beer mugs over plates of rib eye steaks to toast their lead lawyer, Shannon Liss-Riordan, whom they dubbed "Sledgehammer Shannon."

The dinner party got superb service, Liss-Riordan said, which is hardly surprising; she recently filed class-action suits on behalf of waiters and waitresses at the upscale restaurant who have accused management of skimming their tips, too.

Since 2001, Liss-Riordan, a partner in a modest-size law firm in downtown Boston, has brought at least 40 lawsuits on behalf of waiters, bartenders, and other service workers in Massachusetts who say their employers cheated them out of tips.

She took an obscure 1952 state law that protects tip-dependent workers, who can legally be paid less than minimum wage, and has used it to reap millions of dollars in awards and settlements. Lawyers outside Massachusetts have adopted her strategy, including the lawyers who recently won a $100 million award for baristas at Starbucks cafes in California.

A Harvard Law School graduate who helped found a feminist activist group in the early 1990s, Liss-Riordan originally wanted to be a civil rights lawyer. Instead, the Houston native has become something of an avenging angel for workers who rely on customers' generosity as they carry plates of sirloin and scrod, mix mojitos and martinis, and hoist luggage.

"It's hard work," Liss-Riordan, 38, said of such jobs. "It's physically tiring, it's stressful, and you have to be good dealing with people. They work hard for those tips, and part of the problem with the industry is a lot of managers and owners look at the tips and think, `They shouldn't be making that much money.' So they want to take a piece of it, or subsidize their labor costs for other employees."

Her clients speak of her almost reverently. Don Benoit, one of about 40 waiters who successfully sued the former Federalist restaurant in Boston in Suffolk Superior Court last year for failing to give them all of the 21 percent service charge added to bills at private functions, called her "brilliant." A former American Airlines skycap who expects to get about $3,000 in back tips from the airline said Liss-Riordan champions the "kickstand of corporate America."

But critics say she has manipulated an arcane and confusing law to reap a windfall for her clients and firm. If such litigation continues, detractors say, awards could skyrocket as a result of a state law passed this month mandating that employers pay triple damages for violations of so-called wage-and-hour laws. Critics say the suits hurt fragile businesses and, sometimes, her clients' co-workers.

"I have a lot of respect for Shannon, but I do see this cottage industry she's created around the tip statute as becoming abusive toward employers," said Ariel D. Cudkowicz, who has defended many restaurants, hotels, and Gillette Stadium against Liss-Riordan's suits, reaching out-of-court settlements in several. The prospect of large awards, he said, is "very alluring" to plaintiffs and their lawyers. Liss-Riordan's firm keeps one-third of the money it obtains for clients.

Liss-Riordan first made national headlines in the early 1990s when she joined the daughter of writer Alice Walker and helped founded the Third Wave, a nonprofit group that led voter registration drives in the wake of the Anita Hill-Clarence Thomas hearings.

After graduating from Harvard Law in 1996 and clerking for a federal judge in Texas, she joined the firm Pyle, Rome, Lichten & Ehrenberg and has been there since. Her mentor, Harold L. Lichten, a well-known labor and employment lawyer, said she is "the smartest, most pugnacious, and toughest attorney I've ever met."

It is not uncommon for him to arrive at their Tremont Street office in the morning only to find Liss-Riordan at her desk after working through the night, he said, "which is particularly amazing given that she has three kids." Liss-Riordan's husband is a writer and stay-at-home father.

Most of her suits allege violations of a state law that prohibits management at restaurants, bars, and hotels from taking a portion of tips reserved for waiters and bartenders who can legally be paid as little as $2.63 an hour, well below the state's minimum wage of $8 an hour.

Some restaurants say other employees, including managers and maitre d's, deserve a share of tips because they sometimes serve food and drinks and also earn relatively low wages. But Liss-Riordan says that if those workers deserve more money, owners should raise their pay.

Defendants have included the Four Seasons Hotel, the Weston Golf Club, Northeastern University, the Palm, and Ruth's Chris, whose Boston lawyer declined to comment. One of the biggest awards came in 2006 when an Essex County jury ordered Hilltop Steakhouse in Saugus to pay an estimated $2.5 million in damages to wait staff, but both sides settled out of court before the judgment became final.

In 2004, the Legislature expanded the 1952 statute to cover employees outside the food and beverage industries, paving the way for Liss-Riordan's skycaps suit. In that complaint, skycaps contended the airline violated the tips law when it began charging passengers a $2-per-bag fee for curbside check-in service in September 2005. Skycaps testified that tips plunged because many passengers mistakenly thought the workers kept the $2 fee and were reluctant to tip on top of it.

The airline countered that it put up signs specifying that the fee excluded tips. But the jury sided with the plaintiffs, ordering the airline on April 7 to turn over all the fees to the skycaps. They will receive amounts ranging from $3,066 to $64,138, Liss-Riordan said. She has since filed similar suits on behalf of skycaps from United Airlines and US Airways.

Her co-counsel in about half the cases has been Hillary Schwab, a 34-year-old partner at the firm.

Lawyers elsewhere in the country have followed Liss-Riordan's lead. Last month, a San Diego County judge ordered Starbucks to pay at least 120,000 baristas in California more than $100 million in tips and interest to cover gratuities that the company handed over to shift supervisors.

Starbucks condemned the ruling and said the judge did not consider the interests of shift supervisors who "deserve their fair share of the tips." Nonetheless, Liss-Riordan wasted no time filing similar suits in Massachusetts and New York on behalf of baristas there.

Several people in the restaurant and hotel business say such litigation harms the industry. William Sander, general manager of the Fifteen Beacon Hotel, location of the former Federalist restaurant, criticized a December verdict siding with wait staff who said management illegally shared their tips with private dining room coordinators. He said the law was unclear about which employees were entitled to tips.

If restaurants are forced to pay managers more, he said, "you'll end up closing 90 percent of the restaurants in the country."

That's hogwash, said Liss-Riordan.

A well-managed business, she said, "does not dip into tips to make ends meet."

Copyright 2008 Globe Newspaper Company