A Northern Virginia physician was convicted yesterday of performing an illegal abortion on a 17-year-old high school student who later delivered a dead, 22-week-old male fetus in a Springfield motel room.

Dr. Chris Simopoulos, a 42-year-old Greek immigrant, became the first person to be found guilty of abortion charges in Fairfax County since the 1973 Supreme Court ruling that limited the powers of states to restrict the operations.

Circuit Court Judge F. Bruce Bach announced his verdict in the case without comment immediately after the defense and prosecution completed their closing arguments. Both sides had waived presenting the emotion-charged case to a jury and agreed to have the judge rule on it.

Simopoulos is one of only about 10 physicians in the entire country and apparently the first in Virginia to be proscuted on illegal abortion charges since the high court's ruling, according to defense lawyer Roy Lucas, a prominent proabortion attorney.

Simopoulos could receive up to 10 years in prison for the felony conviction.

His lawyer, in asking that he not be sent to prison, called on Bach to give him a suspended sentence. Simopoulos can also expect a disciplinary review by the Virginia State Medical Board that could lead to the lifting of his physician's license. But his lawyers said they expect the board to withhold action until his appeals of yesterday's conviction are completed.

Simopoulos, who has practiced in Northern Virginia for nearly 10 years, showed no emotion when the verdict was announced. He later told reporters that he was "relieved" the trial was over and was confident he will win on appeal.

"We beleive we have good, strong constitutional arguments," Simopoulos said, as he rested against a courtroom table after the trial. "There's not a shred of doubt in our minds that the ruling will be overturned on appeal."

Simopoulos, who has offices in Woodbebridge and Falls Church, was convicted of violating a Virginia law that requires performing second-trimester abortions -- those done after the 13th week of pregnancy -- in a hospital. The prosecution said he performed the abortion on the girl at his American Women's Clinic in Falls Church last November by injecting her with salt solution. The girl, then a high school junior, was five months pregnant at the time.

The defense, in strongly attacking the Virginia abortion law, argued that the hospitalization requirement for second-trimester abortions unconstitutionaly restricts the ability of minors to obtain abortions.

Defense doctors testified that it is safe and medically acceptable to inject the salt solution used in the abortion in patients outside the hospital, to allow them to wait labor pains at home, and to have them come into the hospital for delivery of the fetus.

The defense also produced evidence that Alexandria Hospital and Fairfax Hospital are the only two hospitals in Northern Virginia that perform second-trimester abortions and that both require parental consent for minors.

The girl testified that she was afraid to tell her parents about her pregnancy.

The courts have ruled that minors are not required to get their parents' consent for abortions, and the defense argued that the hospital rules in effect made it possible for the girl to receive the injection there, the defense said. Defense lawyers also contended that the mere injection of the salt solution did not constitute an abortion, which they said occurs only upon the actual delivery of the fetus.

Simopoulos testified he was unaware of the hospital requirement for second second-trimester abortions. He committed "at worst a technical unintentional violation." Lucas said in his closing argument. The lawyer said Simopoulos intended for the girl to deliver the fetus in Fairfax Hospital's emergency room, which could not refuse to treat her once she went into labor.

Prosecutor Robert F. Horan Jr., i n his closing argument, said the evidence showed that Simopoulos performed the abortion outside the hospital when he injected the girl with the salt solution.

"He terminated this pregnancy outside of a hospital," Horan argued. "All the window dressing about what he thought the law meant . . . or whether he agrees with it is quite beside the point." The death of that child was caused by the actions of" Simopoulos, Horan said.

Lucas and Horan clashed repeatedly over the prosecutor's repeated description of the dead fetus as an "unborn child" and "the body." "The state's trying to make this look like a murder case," Lucas charged. "This isn't a right-to-life rally."