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Technical Issues in Checking Contraband Cell Phone Use in Jails and Prisons
By Terry L. Bittner, Director of Security Products, ITT
Published: 04/05/2010

Mobilephone Prompted in part by some sensational incidents in which inmates in prisons and jails used cell phones to plot and carry out crimes, up to and including murder, the United States Senate passed a bill to authorize the jamming of cell phones in prisons last fall. Similar legislation has been proposed in the House. The problem is a real one. In California prisons, for example, 4,130 cell phones were confiscated in the first three quarters of 2009, up from 2,800 for all of 2008.

In the broadest sense, contraband cell phones are a technical problem and eliminating them demands a technical solution. Technology advances have allowed them to be made smaller and more powerful – and easier to conceal. These days phones are half the size of a cigarette pack, and SIM cards, which can be used interchangeably on most cell phones, are smaller than a postage stamp.

Conventional methods of locating them will only become more difficult. Detection systems have shown that general shakedown searches have failed to detect them. Dogs can be trained to detect cell phones and have had some success, but they aren’t foolproof.

The case for jamming is certainly intuitive – if jamming signals could be precisely controlled as advertized. Jamming systems have been used for everything from blinding enemy antiaircraft radars to blocking or attempting to block the Voice of America. By some reports, the Soviets were spending more to jam VOA broadcasts than the United States was spending to transmit them. Jamming is used as a temporary force protection method against Improvised Explosive Devices (IEDs).

Jamming is also largely effective – sometimes too effective. Some systems will not only prevent cell phones from being used in the jail, but near the jail as well. Most of our experience with this effect is from overseas. In both India and Brazil, cell phones up to five kilometers from the prison were jammed by the prison jamming systems. Recently, a prison in Ireland was forced to stop jamming because their system interfered with the legitimate cell phone signals in the hospital across the street from the facility.

Proposed American prison jamming systems also have gaps to avoid interfering with bandwidths used by emergency first responders. Public Safety communications in the 800 MHz band are interleaved with commercial wireless systems, so jamming equipment intended for use in the United States doesn’t jam that band. That’s good for first responders, but could also make the cell phones using that bandwidth, such as Nextel’s, the inmates’ carrier of choice.

And that brings up another problem with jamming – it produces no intelligence. Cell phone signals are blocked, but prison authorities have no idea whether cell phones are present and/or where they are located. Jamming creates the illusion of security. An inmate with a contraband phone on an unjammed bandwidth, or from a dead zone can make calls with relative impunity.

The optimal solution is a system that prevents phones from getting into the prison in the first place. But a system that detects and locates the cell phones inside the prison, alerting authorities to their presence and location, and giving them the option to move immediately to confiscation or to observe them in action to gain intelligence on the movement of contraband is the next best thing. And the system should also have lower or comparable costs to that of jamming equipment.

Radio frequency (RF) detection systems do not require any special legislation. They are already legal, and indeed, are being used in several prisons in the United States. Most systems simply detect the signals emitted by the phones, both when being used in conversations and when they periodically “ping” the nearest cell phone tower. If you leave your phone near a computer or television set, that buzzing sound you intermittently hear is the phone contacting the tower.

RF detection systems consist of a network of receivers deployed throughout the prison that continually scan the entire cell phone spectrum many times a second. Continual scanning makes it nearly impossible to evade detection by keeping calls brief or only turning on the phone when making a call. When a cell phone transmission is detected, special triangulation software immediately pinpoints its location. The system also logs all captured events.

Detection-only systems do not permit users to listen in on the conversations or gather telephone numbers. Systems that do allow for the interception of calls, phone numbers and text messages still require an accurate location so that those in close proximity to the prison are not intercepted (similar to jamming). Any cell phone in the hands of an inmate is contraband, and warrants to tap into the conversations can be obtained. Indeed, gang members operating in a Baltimore prison were nabbed in precisely this manner.

Detection systems allow authorized corrections officers and other authorized officials to carry their own cell phones, the most economical form of communications, within the facility, which would otherwise be blocked by jammers. They also enable officers to target searches, both for cell phones and the other contraband like drugs that the presence of cell phones indicates.

Perhaps the most effective solution combines detection with specially trained dogs. Dogs can be effective in finding contraband phones, but they have certain weak points. Like humans, they can lose interest, especially when much time is spent and nothing is found. Directed searches ensure that they are always hunting where the ducks are, as it were, ensuring they stay alert and enthusiastic. Indeed, a combination of detection and dogs may be the most powerful possible check to contraband cell phones.

Corrections officials have a heavy responsibility in deciding wisely about deterring contraband cell phone use. As the vote in the U.S. Senate suggests, the politically “safe” proposal may be to jam because it is a solution that, in concept, is easy to understand. But jamming devices are being marketed beyond the walls, and the prison contraband may be the camel’s nose inside the tent. Jamming devices are being marketed to churches, theaters, schools, libraries, shopping malls, hotels (where house phone use and its attendant fees have all but disappeared), public transportation, office buildings and restaurants. Public safety officials are already worried about their ability to receive “911” calls, most of which now come from cell phones.

So the technical decisions corrections officials make will have implications far beyond the prison or jail walls.

Editor's Note: Corrections.com author, Terry Bittner, Director of Security Products, ITT Corporation, is responsible for product design, development, and manufacture, and building business opportunities in the law enforcement, government and commercial security markets. A Vietnam Era Veteran, he served in the United States Navy.


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  3. melissam on 04/13/2010:

    This is a very difficult situation. Hopefully in the near future we will have more intense technology making it easier to detect the phones from bringing them into the prison system. An yes phones are becoming more advance and even smaller, making this more of an issue.

  4. oneonone on 04/09/2010:

    If we had the tech. to detect them or the entrance officer doing there job, we would catch more phones coming in and the people bringing them in.

  5. eeg on 04/05/2010:

    There seems to be a problem with corrections officers and free staff being the ones that are supplying these cell phones. The technology exists to at least make it difficult to use this technology but until the real problem is addressed it just putting a bandaid on something that requires serious help.

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