HARRISBURG -- The Pennsylvania Supreme Court has set standards by which murder defendants can prove they are mentally retarded and avoid the death penalty, but the high court also urged the General Assembly to act on its own.

The state Supreme Court said Tuesday -- more than three years after the U.S. Supreme Court banned executions of people who are mentally retarded -- that it would not rely on a "cutoff IQ score."

Instead, it adopted a system that takes into account both "limited intellectual functioning" and "deficiencies in adaptive skills."

Ruling in the case of Joseph Daniel "Joey" Miller, a Steelton man convicted in March 1993 of murdering two women in Dauphin County, the high court unanimously sent the case back to county court for hearings to establish whether Mr. Miller meets the new standard.

His victims, Selina Franklin and Stephanie McDuffey, were found buried in a Harrisburg-area landfill, as was a third woman, Jeanette Thomas. Mr. Miller, 41, confessed to killing Ms. Thomas but has not been charged in her death.

He is also serving life in prison for murdering Kathi Novena Shenck, a woman who he ran over several times with his car and then buried in a dump in neighboring Perry County.

A county judge had vacated the death sentences on the grounds that Mr. Miller was retarded, but the new hearing ordered by the high court could return him to death row.

Dauphin County District Attorney Ed Marsico Jr. said his office will argue that Mr. Miller "functioned at a fairly high level in society," holding several jobs and being married.

"You have to look at the person's life as a whole," Mr. Marsico said. "There's no magic number that should automatically preclude him from being executed."

Mr. Miller's lawyer, Robert Dunham of the Defender Association of Philadelphia, said the Supreme Court's standard of retardation is valid.

"The court is going to look to the diagnostic criteria that professional mental health organizations have established. I think that's entirely appropriate," Mr. Dunham said.

Justice J. Michael Eakin said the Legislature should act "without further delay" to comply with the U.S. Supreme Court's 2002 decision in Atkins v. Virginia. At the time, Pennsylvania was one of 20 states that did not explicitly ban the execution of the mentally retarded.

"Bills have been introduced, but no legislation has been passed to accomplish this. Meanwhile, cases languish and courts await action which has not been forthcoming," Justice Eakin wrote.

Mr. Miller's case involved his post-conviction appeal, so the Supreme Court did not say how the new rules should apply to new murder cases. It's unclear, for instance, whether a judge or jury should determine retardation, or if that should be done before trial or after conviction.