Duhaime's Law Dictionary


Pen Register Definition:

An electronic surveillance device which attaches to a phone line and which registers every number dialed from a specific telephone.

Related Terms: Wire-tapping, Electronic Monitoring

This surveillance device is not as effective as wire-tapping.

In the United States, the term pen register is defined in Federal law as follows (18 USCA §3127):

"The term pen register means a device or process which records or decodes dialing, routing, addressing, or signaling information transmitted by an instrument or facility from which a wire or electronic communication is transmitted, provided, however, that such information shall not include the contents of any communication, but such term does not include any device or process used by a provider or customer of a wire or electronic communication service for billing, or recording as an incident to billing, for communications services provided by such provider or any device or process used by a provider or customer of a wire communication service for cost accounting or other like purposes in the ordinary course of its business"1

pen register

In In Matter of Application of U.S. For an Order Authorizing the Installation and Use of a Pen Register and a Trap & Trace Device on E-Mail, Chief Justice Hogan of the United States District Court, District of Columbia used these words in regards to 18 USCA 3127:

"A pen register may be a process that records outgoing signals from an instrument or facility that transmits electronic communication.

"Our own court, as well as at least one other, has considered the question of whether a pen register and trap and trace device may be used to obtain cell site information that reveals the location of a cell phone user.

"The statute goes on to define trap and trace device to mean a device or process which captures the incoming electronic or other impulses which identify the originating number or other dialing, routing, addressing, and signaling information reasonably likely to identify the source of a wire or electronic communication, provided, however, that such information shall not include the contents of any communication. According to this definition, a trap and trace device may be a process that is used to capture incoming electronic impulses to identify the source of an “electronic communication,” albeit not the contents of that communication.

"These definitions make clear that both a pen register and a trap and trace device may be a process used to gather information relating to electronic communication."

The 2012 edition of CJS reaffirms this statement of law in these words:

"A pen register is a device or process which records or decodes dialing, routing, addressing, or signaling information transmitted by an instrument or facility from which a wire or electronic communication is transmitted. A trap and trace device is a device or process which captures the incoming electronic or other impulses which identify the originating number or other dialing, routing, addressing, and signaling information reasonably likely to identify the source of a wire or electronic communication. In addition to other uses to which the prohibition does not apply, the prohibition does not apply with respect to the use of a pen register or a trap and trace device by a provider of electronic or wire communication service where the consent of the user of that service has been obtained."

In an 1993 Canadian case, R. v Fegan, Justice Finlayson of the Ontario Court of Appeal adopted these words:

"It is our view that there is no reasonable basis for inclusion of the pen register and related devices (such as diode devices used to track the number of an incoming call after the caller has hung up) within the... legislative scheme (which is) primarily directed at protecting privacy of communications; that is, discourse between persons. These devices do not invade the privacy of the communication."

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