Shannon Nixon died at her Altoona, Penn., home on June 27, 1996, of complications from diabetes, including severe dehydration. Her blood sugar level was 18 times the normal level at her death.
In the 7-0 ruling made public Tuesday, Justice Stephen Zappala rejected the defenses that Shannon was a "mature minor" and that taking her to a doctor would have violated her privacy.
Her parents, Dennis and Lorie Nixon, were convicted of involuntary manslaughter in 1997. They were each sentenced to 2 1/2 to five years in prison but have been free during their appeals.
They belong to a Blair County branch of the Faith Tabernacle Church, which advocates faith healing over modern medicine. It also has branches in New Jersey and Philadelphia.
The Nixons based the defense in part on a Tennessee case in which courts ruled authorities could consider factors beyond a child's age, including experience, education and maturity, in deciding when a child could forgo medical treatment.
But Zappala said Pennsylvania lawmakers spelled out situations in which a child can direct his or her care, for example by making exceptions for treatment for pregnancy, drug abuse and venereal disease.
Justice Ralph Cappy filed a separate opinion saying the "mature minor" defense might work in other cases, when a child understood his or her ailment and the possible outcomes of treatment.
The couple has 11 other children. Another child, 8-year-old Clayton, died in 1991 of what authorities said was a treatable ear infection.
Both Blair County District Attorney David Gorman and the Nixons' attorney, Steven Passarello, were in court Tuesday and did not immediately return telephone messages for comment.
Doctors said Shannon would have lived with insulin. Her family prayed over her bed, read from the Bible and, during a trip to church, coated her body with oil.
Authorities have said at least nine Pennsylvania children of Faith Tabernacle churchgoers have died of treatable illnesses since 1983. Last year, a judge in Philadelphia sentenced a couple to 17 years of probation for letting their 22-month-old son, a hemophiliac, bleed to death in 1997. The judge also ordered them to find a doctor for their other children.