The defense formally closed its case yesterday in the second-degree murder and perjury trial of former Washington abortionist Dr. Robert J. Sherman. The trial is in its sixth week in D.C. Superior Court.

Government prosecutors then called to the witness stand three of Sherman's abortion patients to counter defense testimony about procedures and conditions at Sherman's abortion clinic, once located at 1835 I St. NW.

Defense attorney Robert F. Muse had earlier protested to Judge Fred B. Ugast that the government was trying to get "the emotional last word" at the trial, which has been marked at times by dramatic testimony by former patients.

Ugast then agreed to limit the testimony to the degree of care the women received at the clinic, Sherman's treatment of them and the condition of the clinic itself.

One woman, who went to Sherman for a second abortion, testified that when she complained that she felt nauseated and faint after the procedure, Sherman told her to "go outside in the fresh air..." Although Sherman told her the abortion had been complete, the woman testified, she experienced an abortion the following evening at a local hospital.

Another patient testified yesterday that Sherman conducted her abortion in a "small, shabby room" at the clinic.

Sherman, 65, who did not testify at the trial, is charged with the murder of 16-year-old Rita McDowell, who died at D.C. General Hospital on March 8, 1975, four days after she went to Sherman for an abortion. The perjury charges stem from what the government charges, was a coverup of the circumstances of McDowell's death.

The government contends Sherman deliberately performed incomplete abortions, used unsterile instruments and violated medical standards to increase profits at his clinic.

Principal Assistant U.S. Attorney Carl S. Rauh told Judge Ugast yesterday that the government intends to present additional evidence from two medical experts to respond to defense testimony that McDowell's death resulted from grossly negligent treatment at D.C. General, not Sherman's conduct.