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Supreme Court Rule 201(b)(1) establishes the basic scope of discovery in Illinois. It provides:
may obtain by discovery full disclosure regarding any matter relevant to
the subject matter involved in the pending action, whether it relates to the claim or
defense of the party seeking disclosure or of any other party, including the existence,
description, nature, custody, condition, and location of any documents or tangible
things, and the identity and location of persons having knowledge of relevant facts.
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