United States v. LaSalle National Bank

The IRS issued summonses to two banks (defendants) for records of John Gattuso, whose tax liability it was investigating. Federal law authorized the IRS to examine records to verify tax returns or determine liability. The banks refused to comply, and the IRS sought enforcement in federal district court. The IRS attorney testified he hadn't yet decided whether criminal charges were warranted and hadn't made any recommendation to his superiors, but Gattuso argued the investigation was "purely criminal" in nature. The district court and court of appeals agreed with Gattuso that the IRS had improperly used a civil investigation to gather evidence for a criminal case, and the Supreme Court granted certiorari.