BOSTON, JULY 4 -- Two Christian Scientists were convicted of manslaughter today for relying exclusively on their religion's practice of "spiritual healing" to treat their 2 1/2-year-old son, who died of a bowel obstruction.

The Suffolk Superior Court jury's verdicts against David and Ginger Twitchell, lifelong Christian Scientists and parents of two other children, followed three days of deliberations.

The Twitchells showed little reaction, but several jurors left the courtroom sobbing.

The Twitchells could be sentenced to up to 20 years in prison by Judge Sandra Hamlin, who is expected to set a sentencing date on Friday. The judge denied a defense request to poll the eight women and four men in the jury individually on their verdicts.

David Twitchell, 35, in brief remarks to reporters before leaving the courthouse, complained that the court system worked against him and his wife. "Given the {judge's} instructions and the way the prosecution handled it, I don't think they {the jurors} had much choice," he said.

"It doesn't change our faith in God," Twitchell continued. "What challenged our faith was when our child died. This has challenged our faith in the justice system."

The couple's attorney, Rikki Klieman, said she will file an appeal. She denounced the judge's instructions to the jury, saying they were so biased in favor of a guilty verdict that she was surprised the jury took "more than a minute and a half."

John Kiernan, the special prosecutor, said the verdict served to assert the rights of children. He denied, as he has in the past, that the state prosecuted the Twitchells for their religious beliefs.

The verdict, he said, "will certainly send out a message: When a child is in need of medical care -- in addition to prayer -- the responsibility of the parent is to get that medical care." He said the verdict also is important because it makes clear that "every parent has the same obligation," regardless of religious beliefs.

The trial took place about two miles from the Mother Church of The First Church of Christ, Scientist -- the religious denomination founded by Mary Baker Eddy in 1879. The church, which embraces spiritual healing as a central tenet, has been under attack in state courts nationwide in recent years, and a number of similar convictions are on appeal.

Nathan Talbot, a high-ranking church official who has closely monitored the Twitchell case, said the verdict reveals a double standard. Although many children die while in conventional medical care, he said, criminal charges are brought any time a child dies in a Christian Scientist's care.

The church, which established a defense fund for the Twitchells, has succeeded in passing "exemption laws" in many states, including Massachusetts, that generally exempt Christian Scientists from a legal duty to seek help from medical doctors as long as they pursue a course of treatment recognized by the church.

The Twitchells were described by their attorneys and several witnesses as loving parents who conscientiously followed a regimen of help for their son, Robyn, that they believed was both effective and legal.

After the two-month trial, the jurors deliberated about 14 hours over three days. Three times they asked Judge Hamlin for clarification of the state's manslaughter law.

Hamlin told the jury that all parents have a duty to provide "all necessary and proper physical care" and may not rely exclusively on spiritual healing if it would expose a child to risk of serious injury or death.

As a result of the judge's charge, the key issue in the case appeared to be the jury's assessment of Robyn Twitchell's condition in the days leading up to his death. On that score, the extensive testimony at trial provided an array of evidence, some of it conflicting.

Robyn Twitchell died on April 8, 1986, in the family's former Boston home, five days after becoming ill. According to some testimony, the child showed symptoms of serious illness -- he was not eating, he was "moaning in pain" and, at one point, vomited a foul substance that may have been his feces.

But other witnesses, including the Christian Science "practitioner" who cared for the boy, said his condition was alternately better and worse and that he appeared to be much better on the last day of his life, shortly before he died in his father's arms.

Under questioning by the prosecution, Twitchell, who is an administrator for a Christian Science nursing home, admitted that in hindsight he would consider calling a doctor to save his son and acknowledged that he once visited a dentist and received Novocain after prayer alone failed to cure a toothache.

In the teaching of Christian Science, bodily illness is considered a manifestation of ignorance, evil and sin, which must be attacked through prayer. Church officials have said members are "free moral agents" who can choose to consult doctors without penalty, but the defense attorney argued that reliance on spiritual healing alone is central to the faith.