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How aluminum foil could stop warrantless cell phone searches

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Can cops search your cell phone without a warrant? The question is tying up American courts, where judges are struggling to protect personal privacy without denying police a key crime-fighting tool. Meanwhile, smartphones now contain more evidence than ever before — and it’s become easier for suspects to wipe the phone from afar in the time it takes to get a warrant.

The legal question is going to the Supreme Court. But, in the meantime, a law professor is proposing a simple, low-tech solution: when making an arrest, cops should stick the cellphones in a Faraday Bag or simply wrap the phone in aluminum foil. Doing so would give the police time to ask for a warrant to search the phone, and also prevent the suspect from wiping its contents in the meantime.

The idea is set out in a paper by Adam Gershowitz, a William and Mary Law School professor, titled, “Seizing a Cell Phone Incident to Arrest: Data Extraction Devices, Faraday Bags or Aluminum Foil as a Solution to the Warrantless Cell Phone Search Problem.”

The paper, first reported by the Wall Street Journal, discusses situations where police arrest someone and would like to search their phone for more evidence. Under the Fourth Amendment, cops can search a person’s pockets and open containers such as a briefcase, but not closed locations (unless it’s an emergency). Courts, however, disagree on whether a phone (and its contact list, call logs, pictures and so on) is like a briefcase or more like a locked container that requires special permission to search.

Gershowitz noted that some police departments are using a device called the “Universal Forensic Extraction Device,” which can suck up the entire contents of a cell phone in less than 90 seconds so investigators may examine a copy of the contents later on. He adds, however, that the devices are too expensive to provide to every single cop and, that civil liberties groups like ACLU have challenged their legality.

The more low-tech solution is to give each patrol a Faraday Bag, like the ones at right, which block wireless transmissions, and sell for as low as $10. Here’s some for sale on Google:

Faraday Bags

Or poorer police departments can simply turn to Reynolds or another aluminum foil maker:

they can simply buy a roll of aluminum foil for $2 in a grocery store and leave it in their vehicle. When the police seize a phone, they simply have to wrap the phone in a few layers of aluminum foil and the chance of remote wiping of the phone will be almost completely eliminated. [empahsi

From a technical point of view, the plan appears sound given that several layers of foil would work the same way as a Faraday Cage (of course, police might need to unwrap it inside some sort of shielded lab because, as soon as the phone re-established a signal, it might execute a data wipe.)

From a policy standpoint, the plan may also provide a sensible balance (provided police don’t start seizing phones more frequently): it promises to preserve traditional privacy rights of those arrested while also giving police a key tool to, well, foil crime.

12 Responses to “How aluminum foil could stop warrantless cell phone searches”

  1. How about phone erasing everything unless it receives an “All OK” code every 4 hours from a particular server (better yet – an individually tailored encrypted message). Should be enough time to get from Bronx to Brooklyn in NY subway. I see this as a $2/month subscription service.

  2. mfocazio

    One solution is a “panic” unlock code that immediately and without interaction or warning, wipes all data on the phone. It looks like you unlocked the phone, but it’s just a screen shot of the last home screen while underneath, it’s writing zeros to all of the data areas.

    Another option is to have your phone always ready to wipe itself when it detects that it has been “captured” by someone. This would be marketed as an “anti-theft” protection, but in reality it would also be a great way to protect your data from illegal search and seizure.

    Captured mode =
    No radio services at all + Device has not been unlocked for 120 minutes + Device has been immobile for 120 minutes + Device is in darkness

    Other “self destruct” options for when the radio is active could be:

    – Device is outside a defined geo-fence
    – Device is out of range of a certain bluetooth device
    – Device has not touched a particular Wifi network in X hours/minutes

    All are a tad scary, as you could get a “wipe” event unexpectedly, but my point is that I’m not even a developer and I can come up with a more than a few ideas that would work to a degree.

    Or, the other option is for the courts to get their heads out of their asses and realize that a mobile phone is a locked box of personal papers and 4th Amendment applies, and they need damn warrant, always and without exception.

  3. Can’t they just remove the Sim and make sure they make it forget any WiFi? (or take it to a lab where there is a WiFi not saved in the phone). Data connectivity is the key to remotely wiping phones. Everything else stays as it is till it is connected to the network.

  4. Never going to happen – the police want the phone active after the arrest so that any criminal activity can be monitored at the police station. If they block all signals it will be via a sophisticated frequency scanner, which acts like a big net to merely log or re-route the data.