A criminal complaint filed in July accuses Said Farraj, 27, a temporary summer intern at Orrick Herrington & Sutcliffe in Manhattan, of stealing the 400-page plan in June.
He and his brother then tried to sell the plan to defense lawyers for Philip Morris Cos. and other cigarette makers for $2 million, prosecutors said.
Federal prosecutors in New York say tobacco lawyers tipped off the plaintiff's attorneys, who in turn summoned the authorities.
The plan for the case included the plaintiff's trial strategy, anticipated exhibits and other confidential information.
In an e-mail, the brother, Yeazid Farraj, 24, told an undercover FBI agent posing as a tobacco lawyer "that he believed the asking price was a reasonable amount since, in [his] opinion, the defendants, tobacco companies, might very well lose a jury verdict," prosecutors said in their complaint.
The case was first reported by The Smoking Gun Web site. The U.S. attorney's office in Manhattan did not announce the arrest in July and a spokesman did not return a call for comment Thursday.
In a document filed Thursday with the court, Assistant U.S. Attorney Joseph DeMarco said the brothers are now in plea negotiations with prosecutors.
Lawrence Ruggiero, an attorney for Said Farraj, declined to comment.
In the tobacco trial, a trust representing asbestos-related liabilities is attempting to get the tobacco companies to reimburse them for damages they paid.
The case could go to trial within a few weeks.
Other defendants include R.J. Reynolds Tobacco Co., Lorillard Inc., a unit of Loews Corp., and other companies.
Michael Stolper, an attorney with Orrick Herrington, said the firm has cooperated with the federal investigation.
On June 17, when Said Farraj first offered to sell the plan, the trial had been scheduled to proceed on July 21. The case has been delayed due to motions before the 2nd U.S. Circuit Court of Appeals in New York â€“ not as a result of the stolen trial plan, Mr. Stolper said.
The day after Said Farraj left his job with the firm for another at the New York State attorney general's office, he sent the message to a firm representing the tobacco industry, who then informed Orrick Herrington attorneys, Mr. Stolper said.
Said Farraj left the firm because he had a better chance of getting a full-time job after graduation with the attorney general's office, Mr. Stolper said.
"He had good credentials. There was no sign he could be capable of doing this," Mr. Stolper said. "We're surprised."
In an affidavit that is part of the conspiracy and stolen property complaint, FBI agent Trenton Schmatz says Yeazid Farraj, using the alias of "FlyGuy," e-mailed portions of the trial plan to him during the negotiations over price.
FlyGuy said defense lawyers "would have the trial plan within one minute" of the brothers' receipt of the $2 million.
Said Farraj, after being released on $50,000 bond, returned to Quinnipiac College in Connecticut, where he is a third-year law student, according to the Smoking Gun's Web site.
His attorney did not return a call Thursday seeking comment.
A spokesman for Philip Morris declined to comment.
Representatives from other tobacco companies couldn't be reached for comment.