Philadelphia ? In a case that ups the ante for parents who turn a blind eye to underage drinking, a woman could get up to 15 years in prison for a deadly auto accident caused by a teenager who was drunk when he left a party at her house.

Judith McCloskey, 42, will be sentenced next month for involuntary manslaughter. She was convicted in September, 17 months after a 19-year-old man leaving the rowdy gathering crashed his sport utility vehicle, killing himself and two passengers.

Legal experts and activists said they are not aware of another case in which an adult who opened a home to partying teens but did not provide the alcohol was found guilty of manslaughter in a drunken driving death.

“This is a landmark case,” said Wendy Hamilton, president of Mothers Against Drunk Driving. “I think that this sends a very strong message to every parent in the country. There are too many adults who think that drinking underage is a rite of passage. It is not.”

McCloskey acknowledged that she had allowed her two teenage daughters to have a party in her Bangor home, but said she was unaware the youths gathered in her basement were drinking.

The case is the latest in which prosecutors have sought to expand the criminal responsibility of third parties in drug and alcohol deaths.

In August, a New Jersey man was tried on manslaughter charges for a deadly crash caused by a drunken friend. Prosecutors said Kenneth Powell picked up the friend after his arrest on a drunken driving charge and drove him back to his car. Less than an hour later, Michael Pangle got into a head-on collision, killing himself and the other driver.

Powell was acquitted of manslaughter, but the jury deadlocked on lesser charges of vehicular homicide and aggravated assault by automobile.

In many states, adults have gone to jail for buying beer and liquor for minors later involved in drunken accidents or who suffered alcohol poisoning. Parents who allowed the friends of their underage children to drink in their homes have also been prosecuted, but usually on charges that carry little jail time, such as contributing to the delinquency of a minor.

McCloskey’s attorney, Gary Asteak, said the case sets a dangerous precedent.

“It would put parents in the role of being probation officers for their children, and would ultimately leave them responsible for everything their kids do, whether they see them doing it or not,” he said. He plans an appeal.

An adult who bought the kegs for the party pleaded guilty to furnishing minors with alcohol and was fined $1,000.