In New Jersey v. T. L. O., 469 U. S. 325 (1985) , the Court established a two-step inquiry for determining the reasonableness of a school official’s decision to search a student. First, the Court explained, the search must be “ ‘justified at its inception’ ” by the presence of “reasonable grounds for suspecting that the search will turn up evidence that the student has violated or is violating either the law or the rules of the school.” Id., at 342. Second, the search must be “permissible in its scope,” which is achieved “when the measures adopted are reasonably related to the objectives of the search and not excessively intrusive in light of the age and sex of the student and the nature of the infraction.” Ibid. (emphasis added).
The Fourth Amendment “right of the people to be secure in their persons … against unreasonable searches and seizures” generally requires a law enforcement officer to have probable cause for conducting a search. “Probable cause exists where ‘the facts and circumstances within [an officer’s] knowledge and of which [he] had reasonably trustworthy information [are] sufficient in themselves to warrant a man of reasonable caution in the belief ...