A medical expert for the defense at the second degree murder and perjury trial of former Washington abortionist Dr. Robert J. Sherman testified yesterday that in his opinion 16-year-old Rita McDowell was "doing well" until doctors at D.C. General Hospital attempted a medical procedure that he said resulted in irreversible shock.

"After that it was a hopeless case," Dr. Lawrence E. Pierce, chairman of the hematology department at the Washington Hospital Center told a D.C. Superior Court jury.

Pierce, who had reviewed McDowell's medical records, agreed that McDowell was seriously ill when she was taken to D.C. General on March 7, 1975, three days after she went to Sherman's clinic for an abortion. She died in the intensive care unit early the following morning.

Pierce testified that in his opinion McDowell "showed great stamina" and said he would have "a lot of optimism that she was going to go all the way." Critical complications set in, however, Pierce testified, after doctors attempted to reinsert a needle into McDowell's chest in order to monitor her blood circulation.

The defense contends McDowell's death was caused by grossly negligent treatment at D.C. General, not Sherman's conduct. The prosecution, backed by testimony from the city's deputy chief medical examiner, argues that McDowell died as a result of blood poisoning and shock due to an abortion.