Constitutional arguments took a back seat to medical details Wednesday as the Supreme Court heard arguments in a pair of hot-button cases challenging the federal ban on “partial birth abortion.”

Several justices, including Justice Anthony Kennedy, the crucial swing vote on the issue, appeared intensely interested in whether practical alternatives to the controversial procedure exist. Because of the emergency nature of the procedure, Kennedy also indicated that he was concerned that if the law is upheld, a woman who needs the procedure would not be able to challenge the ban quickly enough to avoid being harmed.