BOISE - Idaho could follow Nebraska in banning abortions once a fetus has reached 20 weeks, despite a state attorney general's opinion the bill is unconstitutional - and doctors' concerns that it could force women to deliver babies suffering from rare-but-deadly diseases that leave them little chance of survival outside the womb.

The measure, which relies on disputed evidence of just when humans begin feeling pain, cleared the Republican-dominated Senate State Affairs Committee on a 7-2 vote Wednesday morning after 2 1/2 hours of testimony. It now goes to the full Senate.

Sen. Chuck Winder, the measure's Republican sponsor, assembled a group of out-of-state medical and legal experts to convince the panel that a fetus 20 weeks after fertilization will suffer during an abortion - and that a ban on such procedures will survive the courts. Dr. Ferdinand Salvacion, a professor of anesthesiology from Southern Illinois University, told the committee that surgeons performing medical procedures on fetuses in the womb have begun to use anesthesia.

"By 20 weeks, pain receptors have appeared throughout the body," Salvacion said. "It is also my opinion that the fetus would be subjected to intense, excruciating pain, occurring prior to fetal demise, from abortion procedures used in the second and third trimester."

Over the last decade, Idaho has spent more than $730,000 to defend restrictive abortion laws that were stricken down by the courts. Those costly rulings have prompted Idaho's legislative leaders in recent years to require that abortion-related legislation be reviewed by the Idaho attorney general's office.

Last month, the Idaho attorney general told Winder that modifications would likely be required for his measure to pass constitutional muster.

The measure is "unconstitutional under the Fourteenth Amendment to the United States Constitution insofar as it proscribes some non-therapeutic abortions even before a fetus has reached viability," wrote Steven Olsen, the chief of the agency's civil litigation division.

Evidence of when fetuses begin feeling pain is also disputed, with the American Congress of Obstetricians and Gynecologists saying it knows of no legitimate evidence showing a fetus can ever experience pain. That conclusion is shared by authors of a study from the Royal College of Obstetricians and Gynecologists in London who contend pain perception begins at 24 weeks.

So far, however, the constitutionality of Nebraska's law - and its scientific underpinnings - haven't been challenged in the courts.

That has anti-abortion lawmakers in several other states including Iowa, Indiana, Kentucky, Oklahoma and Florida contemplating similar fetal pain legislation. The goal, proponents say, is to go state-by-state to deny abortion doctors a refuge to perform such procedures.

Teresa Stanton Collett, a law professor at the University of St. Thomas in Minnesota, told the Senate panel that a state's "compelling interest" in protecting fetuses from pain could convince the courts that Idaho's measure is constitutional.

"If there is a single issue in the abortion debate where common ground could be found, one would hope it might be on the issue protecting the unborn from the pain of abortion," Collett said.

The bill, backed by groups ranging from the Idaho Chooses Life anti-abortion group, as well as the Roman Catholic Diocese of Boise, would ban elective procedures after 20 weeks, except in instances where the mother's life is at risk of death or "substantial and irreversible physical impairment" - or when an abortion is necessary to preserve the life of an unborn child such as a twin.

Such abortions are rare in Idaho, with only 6 performed in Idaho in 2009, out of a total 1,650 procedures. Kristen Glundberg-Prossor, a Planned Parenthood of the Great Northwest spokeswoman in Seattle, contends all of the abortions performed after 20 weeks were done to address situations where fetuses had rare conditions such as trisomy 18 that are almost always deadly.

Dr. Glenn Weyhrich, a Boise medical doctor who performs abortion services, said an absolute ban on such procedures after 20 weeks could force a woman to deliver a baby she knows is destined to die, causing deep psychological trauma and suffering, he said.

"In my experience, I've have not had any experience with women who opted to carry the pregnancy (with a fetal anomaly) to term," Weyhrich said. "The way this bill is written, the woman would be obligated to carry those pregnancies to term."

Dr. Sean Patrick Kenney, director of maternal fetal medicine at St. Elizabeth Regional Medical Center in Lincoln, Neb., and a backer of Winder's measure, suggested to the panel that parents have an obligation to make fetuses comfortable as possible until they reach their "natural conclusion," even in instances where they are bound to die after being born.

"Why do we have to give them a choice?" Kenney said. "It's not a choice that needs to be made."