Georgia O'Keeffe went to court yesterday in a dispute over custody of three of her "favorite" paintings, all of them O'Keeffes.

As a result of her suit, the Supreme Court of New Jersey is now trying to decide who owns the three small oils: Barry Snyder, the Princeton art dealer who bought them for $35,000 in 1975; or O'Keeffe, who made them and says that they were stolen from her husband's gallery in 1946.

The outcome of the suit may alter the future legal treatment of stolen artworks.

Possession, it is said, is nine-tenths of the law, but the great age and great fame of Georgia O'Keeffe may, at least in this case, alter that proportion. Now 92 years old, she is one of the best, and best-known, painters in America.

Although the case involves a complex legal history and subtle points of law, New Jersey public television last nigth devoted three hours to the arguments of the lawyers and to O'Keeffe's career.

The three works in question -- "Fragment of Rancho de Taos Church," "Seaweed" and "Cliffs" -- were painted by O'Keeffe half a century ago. She says that they were stolen -- she does not know by whom -- from An American Place, the famous New York gallery which her husband, Alfred Stieglitz, ran until his death in 1946.

No one is claiming that Snyder stole the paintings. His lawyers say he bought them from a man named Ulrich Rank who had inherited them from his father, a physician. Snyder first saw the pictures in the early 1970s in a New York gallery where they were on consignment. Eventually he bought them from their "owner," and took them to his private gallery in Princeton.

In 1976, after learning of the paintings' whereabouts, O'Keeffe contacted the dealer and asked for their return. Snyder refused. O'Keeffe then filed suit, but lost in a lower court when the judge ruled that the six-year statute of limitations on the theft had expired.

When the case first went to court, Snyder's lawyers chose not to contest O'Keeffe's assertion that the paintings had been stolen. But they did not concede that what she said was true. Instead, they based their arguments on the statute of limitations. "Thirty years had passed," one of them said yesterday, "and she had not moved a muscle. She had never reported the thefts to the police." The judge of the lower court ruled in Snyder's favor. t

On appeal, however, that decision was reversed.

A panel of three judges of the Appellate Division of New Jersey's Superior Court ruled 201 that the lower court had been in error; that because the paintings had not been held "openly," the statute of limitations had not begun to run until O'Keeffe first learned of their whereabouts. Since the question of their theft had not been contested in the lower court, the judges -- noting "we perceive no real dispute as to the larcenous origin of" Snyder's "possession" -- ordered that the paintings be returned to O'Keeffe.

The case was then referred to the Supreme Court of New Jersey, where briefs were filed yesterday.

After the appeals court ruled, O'Keeffe said: "It seemed to me a sorry state of affairs if somebody could steal a painting and sell it six years later and prevent the artist from getting it back."

"No one is saying that if you steal a painting and put it in your basement for six years it's yours," Mark Schorr, one of Snyder's lawyers, said yesterday. "This case is far more complex. Is there a statute of limitations? When does it begin to run? When does it expire? Were the works stolen? If so, how do we know? Is O'Keeffe's assertion the only evidence required for her claim to be believed?"

Roger Lowenstein, O'Keeffe's Newark lawyer, yesterday said his client "went wild when she first discovered they'd been stolen. She didn't tell the police -- but in 1946 the police would not have cared about the theft of three modern paintings by someone called O'Keeffe. But she did put the word out. She told all her friends."

The three paintings are now locked away in a New Jersey bank vault. Lowenstein has asked the court to end the litigation and to return them to O'Keeffe. The court also is expected to decide when the statute of limitations had expired," said Schorr. "If the Supreme Court disagrees, we'd at least expect a new trial. O'Keeffe asserts the works were stolen, but we only have her word. She hasn't offered any evidence at all to support that claim."