[Orin Kerr] Was it legal for the FBI to expand the Weiner email search to target Hillary Clinton’s emails?

Hillary Clinton adviser Huma Abedin, right, at the third presidential debate on Oct. 19. (Drew Angerer/Getty Images)

FBI Director James B. Comey recently announced that the FBI had discovered new emails that might be relevant to the investigation of Hillary Clinton’s email server. The emails were discovered in an unrelated case, and the FBI now plans to search through the emails as part of the Clinton server investigation.

Comey’s announcement raises an important legal question: Does expanding the FBI’s investigation from the unrelated case to the Clinton case violate the Fourth Amendment?

We don’t know all the facts yet, so it’s somewhat hard to say. But here’s why the expansion of the investigation might be constitutionally problematic. Consider this a tentative analysis unless and until more facts emerge.

From what I can patch together, the FBI was investigating former congressman Anthony Weiner for potential crimes involving sexting with an underage girl. As part of the investigation, the FBI seized Weiner’s laptop to search it for evidence of the sexting crimes. I would guess, although I haven’t yet been able to confirm, that the FBI obtained a warrant to search Weiner’s computer. The Fourth Amendment would generally require a warrant to search a suspect’s personal computer unless there are special circumstances such as consent that haven’t been mentioned in press reports.

The case connects to Clinton because the laptop happens to have been shared by Weiner and his now-estranged wife, Huma Abedin, who is an an important adviser to Hillary Clinton. In the course of searching Weiner’s laptop, the FBI came across emails in Abedin’s email account that appeared to the agents to be relevant to the Clinton email server case. According to news reports, the FBI now is planning to get a warrant to search the laptop for emails related to the Clinton server case. They haven’t obtained that warrant yet, however, so the Weiner computer has not yet been subject to a comprehensive search.

If these facts so far are accurate, the FBI may have violated the Fourth Amendment in expanding the investigation from Weiner to Clinton. Here’s the problem. If the FBI was searching Weiner’s computer, it presumably had a warrant authorizing the search of the computer only for Weiner’s communications with underage girls. If that is correct, going from that narrow search to a broader search of Clinton’s emails raises two potential problems for the FBI.

The first issue is whether the FBI was permitted to search through Abedin’s email account for records of Weiner’s illegal messages with underage girls. In People v. Herrera, 357 P.3d 1227 (Colo. 2015), the Colorado Supreme Court provided some reason to think that the answer may be “no.” In Herrera, the government had a warrant authorizing the search of a cellphone for messages between the defendant and an undercover officer who had posed as a underage girl. When the police executed the warrant, the officers also searched a folder that contained messages between the defendant and a different (real) underage girl. The court held that searching the folder violated the Fourth Amendment because the only evidence authorized to be seized in the warrant — the messages between the defendant and the undercover officer — weren’t likely to be in the folder containing messages between the defendant and the other girl. I have criticized that reasoning, but it raises questions about whether the FBI could look through Abedin’s account for Weiner’s illegal emails.

There might be similar problems because the alleged Weiner texting crimes apparently occurred in 2016. I gather that the Clinton emails were from her time as secretary of state, which was several years earlier from 2009 to 2013. If I’m right that there was a several-year gap between the warrant crime and the second investigation, it’s not clear the government c