NEWARK, FEB. 4 -- An expert witness told a jury today that the tobacco industry continues to tell the public that smoking hasn't been shown to cause lung cancer even though industry scientists, executives and consultants were acknowledging the opposite in private more than a quarter-century ago.

Dr. Jeffrey E. Harris based his testimony mainly on internal documents from the files of Liggett Group Inc., P. Lorillard Inc., Philip Morris Inc. and Arthur D. Little Inc. of Cambridge, Mass., a leading scientific consulting firm retained by Liggett & Myers, Liggett's tobacco subsidiary. The documents were introduced as evidence in a smoker-death case in U.S. District Court here.

Harris, a physician and economist who is testifying for the plaintiff, said he drew his conclusions partly from an Arthur D. Little memo that said "There are biologically active materials present in cigarette tobacco. These are: a) cancer-causing {and} b) cancer promoting ..." The date on the memo, which is not signed, is March 15, 1961.

"No one at Liggett remembers ever seeing this document," said Alan Hilburg, a spokesman for Liggett. He emphasized that the document came from Little's files, not Liggett's files, and that Harris will be cross-examined on his testimony, probably beginning Friday.

Under questioning by Marc Z. Edell, the lawyer for the late Rose D. Cipollone and her husband, Harris referred to additional documents that showed that a 20-year, $14 million joint research effort by Liggett and Little led to the development in the late 1970s of a a "safe" cigarette.

In the documents, Liggett scientists said that mice painted with smoke tars from the new cigarette -- which used a combination of two additives, palladium and magnesium nitrate -- developed up to 100 percent fewer skin malignancies than when painted with the tars of ordinary cigarettes.

In 1979, after patenting the so-called palladium cigarette, Liggett tried to license at least one overseas tobacco company to sell it, but finally decided in 1981 not to sell it, the documents showed.

Harris testified that there was "no legitimate scientific reason" for not marketing the palladium cigarette.

"We never got any encouragement from the scientific community," said Hilburg, the Liggett spokesman.

Lawyer Edell also introduced: A November 1961 report in which Helmut Wakeham, research director for Philip Morris, listed 15 compounds in cigarette smoke "identified as carcinogens," listed two smoke ingredients as cancer promoters and proposed a research and development program "leading to a minimally acceptable cigarette."

Wakeham's "guestimate" was that by spending $10 million over 7 to 10 years, Philip Morris could achieve "reduction of the general level of carcinogenic substances in smoke ..." He added in the report: "A medically acceptable low-carcinogen cigarette may be possible. Its development would require: time/money/unfaltering determination."

A 1963 memo in which an aide to the surgeon general said he had been told by Charles J. Kensler, the Little executive in charge of biological research for Liggett, that Liggett hadn't published a lot of scientifically worthy materials because of the possibility that some of it "could be used in a lawsuit against them ..."

Two previously confidential documents entered as evidence today concerned a multimillion-dollar American Medical Association research program that tobacco companies funded after the surgeon general's advisory committee issued its first report on smoking and health in January 1964.

An industry document, summarizing the views of company scientists 6 1/2 years later, said they considered "not more than 50 percent of the program was relevant to smoking," and that "little of scientific significance will emerge" from the program.

The second document was written by William Kloepfer Jr., an executive of the Tobacco Institute in Washington, to Institute President Horace R. Kornegay. The subject was Kloepfer's meeting with AMA Executive Director Ernest B. Howard on Sept. 3, 1971.

Kloepfer wrote that Howard "is most anxious to avoid any incident which will create displeasure with AMA among tobacco area Congressmen -- he said AMA needs their support urgently."