A defense attorney for former Washington abortionist Dr. Robert J. Sherman told a D C. Superior Court judge yesterday that Sherman is expected to remain hospitalized until Friday for tests related to heart problems.

Sherman, 65, was rushed by ambulance from the courthouse to George Washington University Hospital at noon Monday after complaining of chest pains. A hospital spokesman said late yesterday afternoon that Sherman is in fair condition and under observation in the coronary care unit.

Closing arguments in Sherman's trial on second-degree murder and perjury charges were postponed Monday morning after a juror abruptly disclosed that she had received threatening late-night telephone calls since last Wednesday. At least one call was related to the case.

There were also indications that the juror, who was excused from the case, alleged that fellow jurors made statements suggesting they had come to conclusions about the case.

The jury, sequestered in a local hotel since Monday at Judge Fred B. Ugast's order, returned to the courthouse yesterday at 1:30 p.m., escorted by deputy U.S. marshals. The jurors were to remain in the courthouse all afternoon, although the trial, now in its seventh week, is not in progress. It was understood that the court planned to question jurors privately and individually about matters that arose Monday.

Meanwhile, at a brief hearing yesterday, defense attorney Robert F. Muse told Ugast that doctors have initially determined that Sherman's chest pains apparently were due to coronary artery disease, not a heart attack.

Ugast, who said he planned to contact Sherman's doctor himself, then adjorned the proceedings "on this point" until 2 p.m. today.

Sherman is charged with murder and perjury in connection with the death in March 1975 of 16-year-old Rita McDowell who died four days after she went to Sherman's clinic at 1835 I St. NW for an abortion.