A Prince George's County Circuit Court judge granted a new trial yesterday to a former high school wrestling coach who was convicted in July of child abuse of a former student who said he was forced to commit a sex act at the coach's apartment in 1983.

Judge G.R. Hovey Johnson ruled that the conviction of Michael John DeSarno, 47, of Beltsville was "tainted" because DeSarno was later acquitted of a similar charge involving a different student. The second student, who was 15 at the time of an alleged August 1984 incident, provided what the judge called "devastating" testimony against DeSarno in the first trial.

Johnson told attorneys that he had "had trouble" allowing the boy to testify against DeSarno's character in the first trial, because the incident the boy described had not been proved in court. But under Maryland law, he said, he was powerless to prevent it. In most states, the boy's testimony would not have been allowed, he said.

The two cases were tried before Johnson on consecutive days, with the same defense attorney and prosecutor but with separate juries. In both cases, DeSarno, who coached wrestling at Hammond High School in Howard County and later at St. John's College High School in Northwest Washington, was accused of hypnotizing the students before telling them to disrobe and perform sex acts. His supporters packed the courtroom at both trials, and let out thunderous cheers when he was acquitted in the second case.

Assistant State's Attorney Thomas McManus said it did not trouble him "in the slightest" to call on the boy to testify in the first trial. "It's not unusual for victims of this type of abuse to have similar stories or to testify in each other's cases," he said.

McManus said he was confident that the boy would be allowed to testify in the new trial, but said he had not yet decided if he would call him.

Defense attorney Joseph DePaul, however, said he did not think Judge Johnson would allow the boy to testify. "The facts of the case are changed now," he said. "We don't have to worry about the boy's testimony."

DeSarno said he was "pleased" with today's ruling. "I didn't do it and I'm going to prove [that] at the new trial," he said.

No trial date has been set.