MILAN — A verdict is expected as soon as Wednesday in a landmark case in which 26 American officials are charged with kidnapping a Muslim cleric from the streets of Milan more than six years ago.

The case is the first of its kind to contest the practice of “extraordinary rendition,” in which terrorism suspects are captured in one country and taken for questioning in another, presumably one more open to coercive interrogation techniques. Widely seen as a referendum on Bush administration fore