Philip Morris USA should pay for annual chest scans for thousands of longtime Marlboro smokers in Massachusetts because the company sold a defective and unreasonably dangerous product, a lawyer for the smokers told jurors at the close of a trial.

"You're about to deliberate about the most dangerous consumer product ever invented," attorney Kevin T. Peters told the panel Tuesday in federal court in Boston. "It's a product intended to addict its users and intended to addict children."

The jury of eight men and two women heard evidence over eight days in the class-action case, which was filed 10 years ago. Members of the class must be at least 50 years old, have purchased Marlboros in Massachusetts and have smoked at least a pack a day for 20 years, for a total of 146,000 cigarettes each.

Company attorneys said smoking cigarettes is dangerous but buyers know the hazards of smoking and the product isn't defective. Government regulators have never found Marlboros to be more dangerous than other brands, they said.

Philip Morris's lawyer Diane P. Sullivan said Tuesday that people have known Marlboros were dangerous for half of a century and aren't buying a defective product. She accused the other side of appealing to jurors' emotions over lung cancer deaths.

"They're trying to get you mad at tobacco companies so you'll ignore the fact that they didn't have the evidence to support their case," Sullivan told the jury. Marlboros would be defective if they exploded and burned your face, she said.

She displayed a picture of cheeseburgers and said if buyers suffer from obesity or high cholesterol, "it doesn't mean cheeseburgers are defective."

"Truth is, addicted or not, people can quit. People make choices," Sullivan told the jury.

"They haven't proved to you that Marlboros are more dangerous than people expect," she said.

The case is one of the few of its kind to win a judge's class-action certification, according to the plaintiffs, and differs from other tobacco suits because the plaintiffs have no apparent symptoms of lung cancer and are not seeking conventional damages.

In a class-action case, one or a handful of people sue on behalf of everyone allegedly harmed in the same way by the same defendant, allowing mass representation rather than many individual cases.

Two other such cases went to trial in the early 2000s, in Louisiana and West Virginia. Philip Morris, a unit of Altria Group Inc., based in Richmond, Virginia, won both. Other cases weren't granted class-action status.

Philip Morris could have made a less carcinogenic Marlboro by using different tobacco and a different filter design but chose not to change the "biggest brand in the world," Peters said.

"Marlboro is what injured my clients," he said. "Marlboro is what made my clients in a category that one out of seven is going to get lung cancer."

Trial exhibits included images of billboards depicting the Marlboro Man, the rugged cowboy with a rope over his shoulder and a cigarette dangling from his mouth. "These were themes that are related to some of the reasons why some people chose to start smoking," psychologist David Hammond testified.

The plaintiffs contend that annual screenings would greatly increase their chances of surviving the disease if it occurs.

More than 36,000 smokers might be eligible members of the class, according to court documents filed several years ago. Current estimates of the class size are under seal. Plaintiffs have estimated that a screening, known as a low-dose computed tomography scan, costs about $500. That puts the bill for 36,000 tests at $18 million a year.

Plaintiffs sought to prove Marlboros' dangers by offering evidence that Philip Morris developed a cigarette with less tar and nicotine decades ago but took it off the market when it didn't sell as well.

If the jury finds Philip Morris made a defective product and agrees low-dose computed tomography scans are an effective way to monitor for signs of cancer, Judge Denise Casper will hear a second phase of the trial focusing on medical monitoring.