A second issue is whether the FBI was permitted to seize the Abedin emails, which were outside the scope of the warrant, and to use them to reopen the investigation into Clinton’s email server. I think this is the bigger legal issue for the FBI. Most courts have treated this as a matter of the “plain view” exception. If the government is searching a computer, and it comes across files that are outside its warrant but are clear evidence of second unrelated crime, the usual government practice is to take those files and use them to get a second warrant to search the computer for the second crime. That’s what the FBI appears to be doing here. They are getting a second warrant after discovering Abedin’s emails because what was likely a first warrant for Weiner’s emails wouldn’t justify the second and broader search. See, e.g., United States v. Carey, 172 F.3d 1268 (10th Cir. 1999).

But if that’s true, there’s a problem: The plain view exception does not allow evidence to be seized outside a warrant unless it is “immediately apparent” upon viewing it that it is evidence of another crime. Just looking quickly at the new evidence, there needs to be probable cause that it is evidence of a second crime to justify its seizure, which would presumably be necessary to apply for the second warrant. See Arizona v. Hicks, 480 U.S. 321 (1987); United States v. Williams, 592 F. 3d 511, 522 (4th Cir. 2010).