NEWARK, FEB. 5 -- Rose D. Cipollone started smoking in 1941, when she was 16. She was found to have lung cancer 40 years later, in 1981, and died in 1984.

In the 1970s, Liggett Group Inc.'s tobacco subsidiary and Arthur D. Little Inc., a consulting firm, were jointly devising a "safer" cigarette, according to company documents. In those documents, Liggett said the cigarette was a startling and undisputed success by the accepted yardstick -- the rate at which malignancies developed on the skin of mice treated with tars from cigarette smoke.

Specifically, the new cigarette reduced the incidence of cancer by up to 100 percent as compared with ordinary cigarettes, according to reports of test results. The "secret" of the new cigarette was the addition of a careful mix of the heavy metal palladium and magnesium nitrate.

If Liggett had begun to sell the palladium cigarette in 1971, and if Cipollone had promptly switched to it (from the Liggett brands Chesterfields and L&Ms she had smoked until then), would the switch have affected her risks of getting lung cancer a decade later?

This question was posed today in U.S. District Court to physician and economist Jeffrey E. Harris, who has contributed to six reports on smoking and health by advisory committees to the surgeon general.

His answer was that her risk of incurring lung cancer would have been reduced by 8 to 17 percent.

The reply was a climactic point in the fourth and final day of Harris' testimony for Antonio Cipollone, Rose Cipollone's husband, in his lawsuit against Liggett, P. Lorillard Inc. and Philip Morris Inc.

Liggett lawyers are expected to attack the claim in cross-examination Tuesday. Philip Morris lawyer Peter K. Bleakley, in the first round of company questioning of Harris this afternoon, established that the witness is not board-certified in any medical speciality. Harris teaches at Harvard Medical School and Massachusetts Institute of Technology.

Harris' focus on the palladium cigarette indicated that it will be a pivotal issue, and that Liggett may emerge as the principal defendant. Rose Cipollone didn't start to smoke Philip Morris and Lorillard brands until after the first surgeon general's health warnings went on all cigarette packages in January 1966.

Liggett internal documents that have been introduced in evidence show that the company had patented and was ready to start selling the cigarette in the late 1970s.

But Harris testified that Liggett could have marketed the new cigarette eight years earlier. He said he based this belief on his review of internal company documents and of tobacco-industry literature, neither of which revealed any disadvantages or problems, and also on what he saw as the company's inadequate spending for research and development.

The palladium cigarette resulted from more than 20 years of study, which was part of a program of smoking-and-health research that cost Liggett about $14.5 million.

Liggett never sold the palladium cigarette. Yesterday, Harris testified that there was no legitimate scientific reason for not having done so.

Liggett spokesman Alan Hilburg said it didn't win support in the scientific community.