Should Police Need a Warrant to Search an Arrestee's Cellphone?

This week, as Mike Riggs noted yesterday, the U.S. Court of Appeals for the 7th Circuit upheld a warrantless search of a cellphone belonging to a suspected meth supplier who had just been arrested. The search in this case was limited to finding the phone's number, which police then used to subpoena the suspect's call history. Writing for the Court, Judge Richard Posner deemed this "a minimally invasive  search" justified by the possibility that the defendant's confederates, learning of his arrest, might attempt to remotely erase the data on his phone. (The two main justifications for allowing a "search incident to arrest" without a warrant are preserving evidence and protecting officers from hidden weapons.) Posner likened obtaining the phone's number to opening an arrestee's diary "to verify his  name and address":

If police are entitled to open a pocket diary to copy the owner's address, they should be  entitled to turn on a cell phone to  learn its number. If allowed to leaf through a pocket address book, as they are, they should be entitled to read the address book in a cell phone. If forbidden to peruse love letters recognized as such found wedged between the pages of the address book, they should be forbidden to read love letters in the files of a cell phone.

At the same time, Posner acknowledged that smartphones are essentially computers, providing a wealth of private information. In this case the government argued that a cellphone is a "container," noting that "a container found on the person of someone who is arrested may be searched as an incident to the arrest even if the arresting officers don't suspect that the container holds a weapon or  contraband." Posner's response:

A modern cell phone is in one aspect a diary writ large. Even when used primarily for business it is quite likely to contain, or  provide ready access  to, a vast body of personal data. The potential invasion of privacy in a search of a cell phone is greater than in a search of a "container" in a conventional sense even when the conventional container is a purse that contains an address book (itself a container) and photos. Judges are becoming aware that a computer (and remember that a modern cellphone is a computer) is not just another purse or address book….An iPhone application called iCam allows you to access your home computer's webcam so that you can survey the inside of your home while you'rea thousand miles away….At the touch of a button a cell phone search becomes a house search, and that is not a search of a "container" in any normal sense of that word, though a house contains data.

In this case, Posner added, "we are quite a distance from the use of the iCam to view what is happening in the bedroom of the owner of the seized cell phone":

We said it was conceivable, not probable,  that a confederate of the defendant would have wiped the data from the defendant's cell phone before the government could obtain a search warrant; and it could be argued that the risk of destruction of evidence was indeed so slight as to be outweighed by  the invasion of privacy from the search. But the "invasion," limited as it was to the cell phone's number, was also slight. 

The cellphone search in this case was less invasive than the one upheld by the California Supreme Court last year, which involved reading a suspected MDMA dealer's text messages. That decision prompted the state legislature to pass a law requiring a warrant for cellphone searches. Although the vote was nearly unanimous, reflecting the widespread sentiment that a cellphone's contents are highly personal, Gov. Jerry Brown vetoed the bill, saying the courts should decide these issues. But if the remote possibility of remote wiping can justify looking through a cellphone without a warrant for evidence of an arrestee's alleged crime, the courts may have a hard time drawing a line between reasonable and unreasonable searches in this context.

If police bust a guy for making meth, can they peruse his text messages (as in the California case) to see if he has set up any deals? Can they open the web browser on his phone to see if he has been looking up synthesis instructions? Can they open every text file, just in case it contains an ingredient list? Can they look at his photos, in case he has proudly taken a picture of his garage lab? And remember: Any rule that applies to a smartphone will apply to all sorts of portable computers. This seems like a situation where a clear statutory rule is preferable to the continuing uncertainty of case-by-case adjudication.