The girlfriend of a slain drug dealer broke off testimony against his accused killers in D.C. Superior Court yesterday, handing the judge a note that asserted she was afraid to continue.

Jennifer Pinkett, 26, earlier had identified two brothers, Nathaniel and James McQueen, as the men who shot Ralph Payne, 37, death in his apartment on 16th Street NW on Oct. 18, 1977.

The 6-foot-6, 230-pound Payne, known as "Big Ralph" was identified by D.C. police after his slaying as an active drug dealer in the area of 14th and T streets NW. The McQueen brothers were arrested later and charged with murder.

Last Friday, according to spectators in the courtroom, Pinkett testified that she was with Payne in his apartment in the Woodner, 3636 16th St. NW, when the slaying occurred.

She identified the McQueen brothers as the two men who burst into the apartment and shot Payne after beating him and pinning his arms to his side.

During her testimony, Pinkett cried as she recounted the murder. The witness chair faced an enlarged diagram of Payne's apartment, propped in the first row of public seats in the courtroom.

Yesterday, Pinkett was scheduled to be cross-examined by lawyers for the McQueen brothers.

Instead, she sent Judge John F. Doyle a note scrawled on a sheet of yellow legal paper saying she was frightened and would not continue testifying.

Before the jurors filed into the courtroom, Pinkett was called before the judge who asked whether she had been threatened since testifying on Friday. She said she had not.

Under questioning by Assistant U.S. Attorney James Hanny, prosecutor in the case, Pinkett said she had traveled to and from the D.C. detention facility in the same bus as the defendants. She is in custody pending the outcome of the case.

She denied, however, that there had been any direct or indirect communication with the defendants since her testimony on Friday.

Hanny finally asked Pinkett whether she realized that her refusal to be cross-examined might result in the acquittal of her boyfriend's accused slayers. She replied that she could not help that.

The trial continued with testimony from other witnesses. Prosecutor Hanny said Pinkett's unwillingness to testifying further would be considered by the judge this morning.