IOWA CITY, Iowa — A divided Iowa Supreme Court today banned judges from imposing life prison sentences without the possibility of parole on juveniles convicted of first-degree murder.The court ruled 4-3 that the sentence amounts to cruel and unusual punishment under the Iowa Constitution. Even juveniles who commit the most heinous crimes should someday have the option of proving to the Iowa Board of Parole that they have been rehabilitated and are fit for release, Justice Brent Appel wrote for the majority.Judges are …