BOISE, Idaho (AP) -- A federal judge has struck down Idaho's law banning abortions after 20 weeks of pregnancy based on beliefs held by physicians and others that the fetus is able to feel pain at that point.

U.S. District Judge B. Lynn Winmill ruled late Wednesday in favor of Jennie Linn McCormack, who was 33 at the time she decided to challenge the state's so-called fetal pain law and other abortion laws.

Idaho was one of seven states to adopt fetal pain laws in 2011, following in the footsteps of Nebraska's approval of the law in 2010. But those laws are no longer the most restrictive. This week, lawmakers in Arkansas overrode a veto of a near-ban on the abortion procedure starting from the 12th week of pregnancy.

In his 42-page decision, Winmill sided with McCormack and her attorney, Richard Hearn, declaring Idaho's fetal pain law places an undue burden on a woman's right to have an abortion. The judge also took the Legislature -- dominated by Republicans in both chambers -- to task for the motives driving adoption of the law, finding that efforts to protect a fetus don't outweigh a women's right to choose.

The judge found "compelling evidence of the legislature's 'improper purpose' in enacting it," Winmill wrote. "The state may not rely on its interest in the potential life of the fetus to place a substantial obstacle to abortion before viability in women's paths," he said.

The ruling also finds unconstitutional at least two other Idaho laws dealing with abortion that Hearn and McCormack also challenged.

One is Idaho's requirement that first-trimester abortions be performed by a physician in a staffed office or clinic, a law that makes most drug-induced abortions, such as RU-486, illegal. The ruling also targets a law requiring that second-trimester abortions be performed in a hospital and a statute that criminalizes the woman in some cases for undergoing the procedure.

"Historically, abortion statutes sought to protect pregnant females from third parties providing dangerous abortions," Winmill wrote. "As a result, most states' abortion laws traditionally criminalized the behavior of third parties to protect the health of pregnant women -- they did not punish women for obtaining an abortion. By punishing women, Idaho's abortion statute is therefore unusual."

McCormack originally filed her lawsuit in federal court against Bannock County's prosecuting attorney on grounds the new fetal pain law was unconstitutional. She initially sought class-action status against prosecutor Mark Hiedeman, who filed criminal charges against her alleging she had an illegal abortion.

McCormack was charged after police began investigating after finding a fetus in a box in January 2011. An autopsy determined it was between five and six months gestation. Police said McCormack told them she didn't have enough money to go to a licensed medical professional, so her sister helped her access abortion-inducing drugs online.

A judge later dismissed the criminal case without prejudice for lack of evidence, but left open the possibility for prosecutors to refile.

In her lawsuit, McCormack challenged the lack of access to abortions for women in her region, as well as the ban on abortions after 20 weeks.

She noted there are no elective-abortion providers in southeastern Idaho, forcing women seeking the procedure to travel elsewhere.

McCormack was unmarried and unemployed at the time of her pregnancy -- with an income of $200 to $250 a month -- and already had three children. She couldn't afford the time or money it would take to travel to Salt Lake City to get an abortion, the lawsuit says.

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