An anonymous reader writes: The U.S. Court of Appeals for the 2nd Circuit last week reversed a tax evasion conviction against an accountant because the government had used data from his computers that were seized under a warrant targeting different suspects. The Fourth Amendment, the court pointed out, 'prevents the seizure of one thing under a warrant describing another.' Law enforcement originally made copies of his hard drives and during off-site processing, separated his personal files from data related to the original warrant. However, 1.5 years later, the government sifted through his personal files and used what it found to build a case against him. The appeals court held that '[i]f the Government could seize and retain non-responsive electronic records indefinitely, so it could search them whenever it later developed probable cause, every warrant to search for particular electronic data would become, in essence, a general warrant', which the Fourth Amendment protects against. The EFF hopes that the outcome of this appeal will have implications for the NSA's dragnet surveillance practice.