A 35-year-old Northwest Washington man has been arrested and charged with sending a threatening letter to D.C. Superior Court Judge Robert M. Scott that vowed "revenge when you least expect it," according to the FBI and court documents.

An FBI spokesman said there apparently is no connection between the man and the ongoing murder trial of 10 persons charged with the murder of Catherine L. Fuller, over which Scott is presiding. The letter "just appears to be a random threat," the spokesman said.

Dennis Henderson was arrested about 8:30 p.m. Wednesday at his home at 1678-B Euclid St. NW by agents from the FBI's Washington field office and members of the D.C. police department's intelligence division. The arrest concluded a joint investigation that began when Scott received the letter Nov. 7, the spokesman said.

Henderson, a former systems analyst with the Northwest Washington accounting firm of Peat, Marwick, Mitchell & Co., was charged with mailing a threatening letter, a felony that carries a maximum penalty of five years in prison and a $250,000 fine, according to the spokesman and documents filed in D.C. Superior Court.

He appeared yesterday in D.C. Superior Court before U.S. Magistrate Patrick J. Tignor and was ordered held without bond pending a hearing today in U.S. District Court.

According to an FBI affidavit filed in D.C. Superior Court that included a text of the letter, the letter was signed in the name of Henderson's wife and was sent through the mail to Scott's chambers at the courthouse, at 500 Indiana Ave. NW.

The letter, according to the affidavit, contains racial slurs and states that the sender is seeking "revenge" for the "sarcastic remark you made to me on the bench." The FBI spokesman said their investigation has turned up no evidence that Henderson, his wife or any of his acquaintances have ever appeared before Scott.

The affidavit says that FBI technicians found fingerprints on the letter that matched "the known prints" of Henderson. In addition, the letter contained typed impressions that matched a memorandum created at Peat, Marwick, Mitchell & Co., where Henderson was employed from July 1984 until June 28, 1985, the affidavit states.

Henderson currently is unemployed, has an unspecified "skull injury" for which he takes medication and shows signs of drug abuse, according to court papers filed by the city's bail agency.

The FBI spokesman said he does not know why the letter was sent in the name of Henderson's wife, who he described as "a hard-working secretary."

Scott, 64, who was appointed to the bench by President Jimmy Carter in 1977, said yesterday that "you get them [threats] every once in a while, but I'm relieved he's been arrested."