Denis O'Brien spent 6 1/2 years earning his doctorate in pharmacology at the University of Virginia here, but it is the law -- not the pharmacy -- that may have taught the 34-year-old graduate student his most lasting lesson.

Embroiled in a spat with a local restaurant over a misplaced food-and-drink check, O'Brien was taken by police before a magistrate and later filed a lawsuit against the restaurant, which was dismissed. The restaurant then sued O'Brien under Virginia's "long-arm statute" and 2 1/2 years after the incident won a $60,000 judgment against him -- without his knowledge, he says -- after he had moved on to a fellowship at Harvard University.

"I've been blindsided," said O'Brien, who still is battling the judgment in Massachusetts, where the restaurant owner is attempting to collect. O'Brien, who says he learned of the judgment only when he happened to call a friend at the University of Virginia, adds that his bank account falls far short of satisfying any such court order.

The ongoing feud between O'Brien and the restaurant, The Mousetrap, located across the street from Mr. Jefferson's venerable, tree-shaded university, has become one of the most acrimonious and long-running incidents in "town -- gown relations" in recent local memory.

"I don't know whether I would have been as persistent as this fellow," sighs Mousetrap owner Diane Brubaker, who says that the case's notoriety has mushroomed into "a matter of principle" and a "personal obligation" on her part to win on behalf of herself and her business.

This is all a long way from the moment on Feb. 29, 1980, when O'Brien, looking for some friends, entered The Mousetrap and was handed a small, red restaurant check used by the establishment to record food or beverages consumed.

O'Brien, who says he is "nearsighted and absentminded," says he turned to leave two or three minutes later only to discover he had misplaced the check. The cashier informed him that Mousetrap policy required that customers who lose their checks pay a $5 fee. O'Brien refused.

Accounts differ about who became rude, insolent and hostile to whom. But in a letter to the lawyer he subsequently hired, O'Brien said that he was ordered by restaurant manager Christopher Wren to locate the ticket or pay the fee. "I told him I was not in the habit of taking orders or crawling around on the floors of restaurants looking for red tickets," O'Brien wrote.

Lawyers for the restaurant, noting that the fee policy was plainly stated both on the check and on a display board at the entrance, accused O'Brien of "getting immense enjoyment" out of the frustration they alleged he was causing the cashier.

Charlottesville police were called and O'Brien was escorted to headquarters, where a local magistrate refused to issue an arrest warrant over, in O'Brien's words, "a two-cent piece of paper."

But the battle, which might have ended then, was just beginning.

In a letter to Brubaker some two weeks later, O'Brien -- raising the possibility of a lawsuit for alleged defamation and false arrest -- demanded a public apology "worded to my satisfaction and printed at your expense" in local newspapers, plus a "reasonable monetary indemnity."

Instead, he received a scathing reply from Brubaker's attorney, prominent Charlottesville lawyer John C. Lowe, advising: "You would be very foolish to get a lawyer who is merely good. You had better get a superb lawyer if you are to avoid serious liability and expense to yourself."

Undeterred, O'Brien hired David C. Landin of the prestigious Virginia law firm McGuire, Woods & Battle and, on Sept. 12, 1980, filed a complaint in Circuit Court seeking $45,000 in damages. A parallel complaint, filed three days later in U.S. District Court, asked $100,000.

The complaints, however, derailed. Circuit Court Judge Herbert A. Pickford agreed with Lowe that O'Brien's defamation charge was too vague under Virginia law and that a false-arrest allegation was spurious because no arrest had occurred.

In May 1981, Pickford gave O'Brien 21 days to amend his complaint, but, for reasons that remain unclear, no amended complaint was filed. "I wish I knew why," says O'Brien. Landin, citing lawyer-client confidentiality, says he is unable to discuss the case.

Meanwhile, in a "Dear Denis" letter on July 15 of last year, Landin raised doubts about proceeding with the complaints. "I am also, candidly, of the opinion that there is a clear possibility that we could lose the case entirely," Landin wrote. He estimated that O'Brien would need to win a judgment of $9,000 "before we would even break even on the time spent."

Last November, Pickford permitted Landin to withdraw from the case, but not before the judge had dismissed a request by O'Brien for a final judgment against The Mousetrap, effectively ending O'Brien's quest in state court.

O'Brien persisted for a short time, representing himself in federal court, but in January of this year a U.S. District judge, following Pickford's lead, threw out O'Brien's complaints. O'Brien says he believed that ended the dispute.

O'Brien, his studies complete, left Virginia and took up a position as a post-doctoral fellow at the Harvard University Biological Laboratories. He also, he says, left his forwarding address with the post office here and with the Circuit Court.

In February, The Mousetrap snapped back.

In a complaint filed in Circuit Court, Lowe asked $330,000 in damages, alleging O'Brien had "grossly distorted the facts of the incident" with "malicious intent" to injure the Mousetrap's reputation.

Further, said Lowe's complaint on behalf of the restaurant, O'Brien had said in a deposition that he found the red ticket in his shirt pocket as he was leaving the magistrate's office and tore it up without telling the restaurant, the magistrate or the police.

To pursue the case, Lowe next availed himself of Virginia's "long-arm statute." While in-state residents generally must be served notice of a suit in person or through a family member, nonresidents may be served in certain cases via the Virginia Secretary of the Commonwealth, who acts by law as their agent.

Lowe duly delivered copies of the complaint, along with O'Brien's forwarding address, to the state capital and received in return an affidavit of compliance from the Secretary of the Commonwealth. Although the Secretary's office forwarded the complaint to O'Brien at his last known address by registered mail, as required under Virginia law, the letter was returned unclaimed in March. O'Brien says that he was unaware of the letter or the suit.

"We followed the law, as far as I can determine, precisely," says Lowe.

O'Brien, not surprisingly, offers a different view. "My 14th Amendment right to due process has been violated," he complains, adding that although he changed residences in the Boston area in March, he again left a forwarding address. "And they could have reached me anytime at the Harvard lab."

With O'Brien nowhere in sight, Judge Pickford eventually ruled in the restaurant's favor. In a one-day trial on June 15, a jury awarded The Mousetrap $52,400 in compensatory damages and $7,600 as a punitive measure for what Pickford characterized as O'Brien's "deliberate, willful, wanton and malicious conduct."

The verdict was reached, Pickford wrote, after O'Brien had been "properly served under Virginia law at his place of residence in Massachusetts, and after having been given timely and proper notice of the trial dates of this case."

"He doesn't have the money to satisfy a $60,000 judgment and he shouldn't have to," says lawyer Barbara Jackins, hired by O'Brien to fight the restaurant's attempts to enforce the judgment through Massachusetts courts.

"In a way," says Lowe, "I hope the case will be retried . . . . I'd like another crack at him. I think he got away really very cheap."