The mother and sister of one of the defendants convicted in the recent Catherine Fuller murder case have been charged with assaulting two neighbors during an argument that apparently stemmed from the trial's outcome, according to documents filed in D.C. Superior Court.

In sworn complaints, Louise Sinclair of 822 Ninth St. NE and her daughter Betty Sinclair alleged that Mary Lee Overton, 47, and Mary Phyllis Overton, 27, attacked them with sticks in the Sinclair front yard during an altercation last Friday night.

The Sinclairs live across the street from Russell (Bobo) Overton, Mary Lee Overton's 26-year-old son who was found guilty on murder charges along with seven other defendants in the brutal Oct. 1, 1984, slaying of Catherine Fuller in an alley near her Northeast home. The D.C. Superior Court jury was first unable to decide charges against Russell Overton, but on Dec. 18 found him guilty of first-degree murder, robbery and kidnaping in the highly publicized trial. Overton is scheduled to be sentenced next month.

The court papers charged that the attack occurred "on account of [the Sinclairs] performing [their] official duty as witness in the Superior Court of the District of Columbia." According to Assistant U.S. Attorney Jerry S. Goren, who prosecuted the Fuller case, the Sinclairs were identified as possible witnesses but were never called to the stand.

The Sinclairs alleged that during the attack, Betty Sinclair, 23, who is six months pregnant, was struck in the left side of the face with a cane or an umbrella. Her mother said she was taken to Providence Hospital for treatment and released. Louise Sinclair said she was inside her home when the argument started and did not know what prompted it but that it related to the trial.

According to court papers, the Overtons were charged with assault with a dangerous weapon and obstruction of justice. Patrick Hand, Mary Lee Overton's lawyer, declined to comment yesterday and neither she nor Mary Phyllis Overton could be reached for comment.

Russell Overton and his sister Mary were raised by their grandmother Edna Adams at her home at 821 Ninth St. NE.

Edna Adams, who was inside her house at the time, said the scuffle apparently started with threats exchanged between Mary Phyllis and the younger Sinclair. She said when she emerged from the house a bottle hurled from across the street struck her in the arm.

"I saw them fussing but I didn't see any fighting. I went over there and got my daughter and told her to come home. It was just a mess going on over there," Adams said.

The month-long trial involved the largest number of defendants ever prosecuted in a single murder case in the District and attracted many residents who knew both Fuller, and members of a loosely knit gang called the 8th and H Street Crew who were accused of her death.

Several prosecution witnesses were friends or acquaintances of the defendants, and also lived in the neighborhood.

Louise Sinclair told a reporter yesterday that she and her daughter have known the Overtons for at least five years and were close to the family.

"They [the prosecutors] asked us questions but not concerning Russell Overton," Louise Sinclair said yesterday. "She [Mary Lee Overton] knew I never took the witness stand in the grand jury or in the trial."

Goren, explaining why the Sinclairs were not called to testify, said, "We announced more than 60 witness and we called less than half. For a case like this that's not unusual at all."

The elder Overton, a nurse who lives at 3223 Farmington Dr., Chevy Chase, and her daughter, who is unemployed, were released Friday night on their own recognizance in lieu of $2,000 bond each. A preliminary trial date was set for Jan. 23. As a condition of their release, the Overtons were ordered to stay away from the Sinclairs.