WASHINGTON — The Supreme Court ruled today that a school’s strip search of an Arizona teenage girl accused of having prescription-strength ibuprofen was illegal.

In an 8-1 ruling, the justices said school officials violated the law with their search of Savana Redding [pictured] in the rural eastern Arizona town of Safford.

Redding, who now attends college, was 13 when officials at Safford Middle School ordered her to remove her clothes and shake out her underwear because they were looking for pills — the equivalent of two Advils. The district bans prescription and over-the-counter drugs and the school was acting on a tip from another student.

“What was missing from the suspected facts that pointed to Savana was any indication of danger to the students from the power of the drugs or their quantity, and any reason to suppose that Savana was carrying pills in her underwear,” Justice David Souter wrote in the majority opinion. “We think that the combination of these deficiencies was fatal to finding the search reasonable.”

In a dissent, Justice Clarence Thomas found the search legal and said the court previously had given school officials “considerable leeway” under the Fourth Amendment in school settings.

Officials had searched the girl’s backpack and found nothing, Thomas said. “It was eminently reasonable to conclude the backpack was empty because Redding was secreting the pills in a place should thought no one would look,” Thomas said.

Thomas warned that the majority’s decision could backfire. “Redding would not have been the first person to conceal pills in her undergarments,” he said. “Nor will she be the last after today’s decision, which announces the safest place to secrete contraband in school.”

The court also ruled the officials cannot be held liable in a lawsuit for the search. Different judges around the nation have come to different conclusions about immunity for school officials in strip searches, which leads the Supreme Court to “counsel doubt that we were sufficiently clear in the prior statement of law,” Souter said.

“We think these differences of opinion from our own are substantial enough to require immunity for the school officials in this case,” Souter said.

The justices also said the lower courts would have to determine whether the Safford United School District No. 1 could be held liable.

A schoolmate had accused Redding, then an eighth-grade student, of giving her pills.

The school’s vice principal, Kerry Wilson, took Redding to his office to search her backpack. When nothing was found, Redding was taken to a nurse’s office where she says she was ordered to take off her shirt and pants. Redding said they then told her to move her bra to the side and to stretch her underwear waistband, exposing her breasts and pelvic area. No pills were found.

A federal magistrate dismissed a suit by Redding and her mother, April. An appeals panel agreed that the search didn’t violate her rights. But last July, a full panel of the 9th U.S. Circuit Court of Appeals found the search was “an invasion of constitutional rights” and that Wilson could be found personally liable.

Justices John Paul Stevens and Ruth Bader Ginsburg dissented from the portion of the ruling saying that Wilson could not be held financially liable.

“Wilson’s treatment of Redding was abusive and it was not reasonable for him to believe that the law permitted it,” Ginsburg said.

The case is Safford Unified School District v. April Redding, 08-479.