Lawyers who represented the plaintiffs in a Mississippi tobacco-liability trial charged yesterday that at least one "paid agent of the American Tobacco Co. illegally and improperly contacted" some of the Mississippi jurors who deadlocked in the case last month.

In papers filed in Holmes County Circuit Court in Lexington, Miss., the lawyers said they have affidavits documenting that the unidentified agents "at least attempted to improperly influence certain jurors during {the} trial."

This "misconduct irreparably damaged" their clients -- the widow and family of Nathan H. Horton, who was a smoker of Pall Mall cigarettes -- "and prevented them from obtaining a fair trial," the lawyers said.

Separately, sources said the Mississippi Highway Patrol has begun a criminal investigation of the charges at the request of Holmes County District Attorney Frank Carleton.

Daniel A. Conforti, public information director of American Tobacco, said yesterday that "there was absolutely no tampering by American Tobacco with the Horton jury."

The Horton case had drawn wide attention, mostly because it was thought to have a reasonable chance of ending a winning streak in which no tobacco company has ever paid a penny to an injured smoker.

To return a verdict for the Hortons under Mississippi laws, only 9 of the 12 jurors had to conclude that American Tobacco was as little as 1 percent responsible for Nathan Horton's emphysema and for the lung cancer that killed him a year ago, when he was 50 years old.

But on Jan. 29, after the jurors had deliberated for approximately 11 hours, Judge Gray Evans declared a mistrial, saying that the jurors were hopelessly split, 7 to 5. He was barred by law from inquiring which side had the majority.

In one of the two motions filed yesterday, the Horton lawyers asked the judge to order the defendants -- American and New Deal Candy & Tobacco Co., a cigarette distributor -- to produce:

The name, address and phone number "of each person hired or paid (as a 'jury consultant' or otherwise) to assist either defendants or their attorneys in trial preparation or at the trial."

"The sum of money paid or owing to each person so hired."

"All records of the defendants, their attorneys and their agents which evidence these sums paid or owing."

American Tobacco's national law firm, Chadbourne & Parke of New York, retained Upshaw, Williams, Biggers, Page & Kruger of Greenwood, Miss., to assist in the trial. James E. Upshaw was the lead defense counsel and was assisted by lawyers from at least two other Mississippi firms.

Upshaw denounced yesterday's action as "a pathetic, pitiful ... absolutely incredible ploy."

He predicted that "the investigation will clear the American Tobacco Co. of any wrongdoing" and said that a "full investigation" will show that "persons sympathetic to the plaintiff ... attempted to influence and intimidate the jury."

In the other motion filed yesterday, the plaintiffs' lawyers -- Don L. Davis of Austin, Tex.; Frederick B. Clark and Jack F. Dunbar of Greenwood, Miss., and Pat M. Barrett Jr. and Don Barrett of Lexington -- asked Evans to rule the defendants liable and to set a trial "solely on the issue of damages."

In the alternative, the motion said, Evans could impose a fine that would "deter such reprehensible conduct" when the case goes to trial a second time. Horton's lawyers have said they would file for a new trial.

No matter which course the judge may decide to follow, the motion said, he should assess the defense "a reasonable sum" as compensation to Hortons' lawyers for their fees and expenses.

Upshaw called the motions that were presented "a desperate attempt to prejudice the jury for the next trial" with adverse national publicity, and he described the affidavits as "laughable."