A Prince George's County judge ruled yesterday that a statement allegedly made by accused murderer Ronald Q. Ellis that he killed six persons may not be used by prosecutors when Ellis goes on trial.

A sheriff's deputy, Morris Ephraim, testified at a hearing before Circuit Judge Jacob S. Levin that Ellis, who is charged with shooting to death his wife, two daughters and three other persons in his Camp Springs home, made the assertion to him in the county jail Sept. 15.

Ephraim testified he had given Ellis court papers listing eight separate legal grounds for seeking the death penalty in the six killings and asked Ellis, who had just read the documents, "Do you have any questions?"

"Ellis said, 'Why eight death penalties? I only killed six people,' " Ephraim told the judge.

Judge Levin ruled that the statement may not be used at Ellis' trial, scheduled to begin Nov. 30, because it was taken in "blatant violation" of Ellis' rights. Ellis' attorney, R. Kenneth Mundy, argued that the deputy failed to advise Ellis of his constitutional rights before questioning him.

Ephraim also testified that Ellis said of the chief Prince George's County prosecutor, State's Attorney Arthur A. Marshall Jr., "Arthur Marshall is really out to get my a--, ain't he?"

Levin ruled that none of Ephraim's testimony may be used at the trial.