In New Jersey last month, the insurance company for a house painter who downed a bottle of Scotch with a friend paid $72,500 to a woman later injured by the drunken friend in a car crash. The painter was nowhere near the accident, but the New Jersey Supreme Court held him partially liable because he served the drinks.

In Massachusetts last August, the Supreme Judicial Court held the town of Ware liable in the deaths of Mark Irwin and his infant daughter, and in the injuries of his wife, Debbie, and son Steven. Two town police officers had flagged down the drunk driver who later crashed into the Irwins' car, but they had failed to take him off the road.

In Missouri last September, a tavern that gave away beer and a radio station that advertised the promotion paid a $92,000 settlement to a couple whose son was killed by a drunk driver who had patronized the bar.

These landmark court cases and similar ones in other states have opened a new battleground in the nationwide crusade against drunken driving and sparked new debate over who should pay for drunken-driving accidents. The new cases pin blame for injuries on those who serve alcohol, those who advertise it and even on towns whose policemen fail to arrest drunk drivers.

The cases come at a time when dozens of states have toughened drunken-driving penalties and the federal government is forcing states to raise the drinking age to 21 or face a cutoff of federal highway funds. More than half of the nation's 125,000 highway deaths a year are alcohol-related.

Dram shop laws, which hold bars and restaurants liable for accidents that result from serving liquor to minors or visibly intoxicated adults, are "a top legislative priority," said Ann Seymour, a spokesman for Mothers Against Drunk Driving (MADD). "We are encouraging our chapters in 47 states to establish new dram shop laws and broaden the scope of existing laws."

The New Jersey decision, which extends dram-shop liability to ordinary citizens serving drinks in their homes, "is precedent-setting and should be extended to all states," she said.

Dram shop laws are on the books in 23 states. Another 18, plus the District of Columbia, allow damage suits against bars and restaurants under common law. Others, including Virginia and Maryland, hold that a third party can't be blamed.

Two states, Oregon and New Mexico, have enacted "host-liability" laws that, like New Jersey's court decision, allow people who serve alcohol to visibly drunk friends to be sued for damages. No case law has resulted in those states, however, according to Victor Colman, a dram shop expert with the Prevention Research Center in Berkeley, Calif.

Last July, an ordinance holding adults liable for use of alcohol and drugs by minors in their home went into effect in Dade County, Fla., which includes Miami. The Florida Supreme Court had ruled earlier that a bar owner could be held liable for injuries caused by a minor who had obtained liquor at the bar.

Backlashes are a danger, however. Social host liability is "political dynamite," Colman said.

Two state legislatures, in California and Minnesota, barred host liability after popular outcries against court decisions. The 1978 California Supreme Court case had upheld damages against a manager of a San Mateo apartment house after he gave a cocktail party for tenants. One of them got drunk and caused a car crash.

In New Jersey, bills have been filed to overturn the court decision and the legislature has appointed a commission to hold public hearings. "Am I my brother's keeper?" asked Assemblyman Robert Hollenbeck, a sponsor of a bill to bar suits against hosts. "How can I stop him from drinking? How can you tell a guy you're playing cards with, 'Hey you've had more than one'? "

Law enforcement officials applaud the decision. "The host liability ruling has had a sobering effect," said Col. Clinton Pagano, superintendent of the New Jersey State Police. The decision, coupled with new penalties setting a minimum $3,200 fine for drunken driving, has contributed to a "dramatic drop in highway deaths," he said.

According to state police figures, in 1983 alcohol was involved in 53 percent of fatal accidents where tests were taken. In 1984, it dropped to 25 percent.

Liquor sales at bars and restaurants were down 35 percent in 1984 from 1983, according to Carmen Giletto, president of the New Jersey Licensed Beverage Association. "There's a neo-prohibitionist movement," he said. "They want to stop people from drinking, period."

A survey of 75 New Jersey companies found that 60 percent banned alcohol or imposed new limits on its consumption at office Christmas parties over the past holiday. Concessionaires at Giants Stadium have stopped selling beer during the last quarter of a game.

Reaction to the Massachusetts decision, which held that cities can be made to pay for deaths and injuries if their policemen fail to remove drunk drivers from the highways, has been strong but the repercussions are not measurable.

Demetrious Moschos, an attorney for the Massachusetts Municipal Association, said, "We are concerned that this new ruling will be used to bring on an onslaught of cases against municipalities."

In Missouri, the radio station that advertised the beer-giveaway, KKCI-FM in Liberty, settled out of court, thus avoiding legal precedent.

Overall, the third-party cases are causing consternation among insurers. Insurance rates for New Jersey's bars and restaurants have tripled in the last few years. Now legislators fear that homeowners' insurance will rise, too.