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A device that decodes or records electronic impulses, allowing outgoing numbers from a telephone to be identified.
The use of pen registers is governed by a 1986 federal statute, Pen Registers and Trap and Trace Devices (18 U.S.C.A. §§ 3121–3127). The statute also governs the use of trap devices, which are used to identify the originating number from which the wire or electronic communications were transmitted. Neither device enables the listening or recording of the actual communication.
In Smith v. Maryland, 442 U.S. 735, 99 S. Ct. 2577, 61 L. Ed. 2d 220 (1979), the U.S. Supreme Court upheld the constitutionality of the use of pen registers, declaring that the use of a pen register is not an invasion of privacy. In the Smith case, Patricia McDonough, the victim of a Robbery, began receiving threatening and obscene telephone calls from a man identifying himself as the robber. In one instance the man asked her to step out on her porch, and when she did, she identified the car that she had previously described to the police as belonging to the robber. The police traced the license plate number and learned that Smith was the registered owner. With this information the police asked the telephone company to install a pen register at its office to record the numbers dialed from Smith's telephone. The register revealed that a call was placed from Smith's residence to McDonough's telephone, and with this information, along with other evidence, the police obtained a warrant to search Smith's residence. During the search the police found Smith's telephone book open to the page where McDonough's name and address appeared. Smith was arrested, and McDonough identified him from a six-man lineup as the man who had robbed her.
Smith asserted that the installation of the pen register violated his constitutional rights and that "all fruits derived from the pen register" should be suppressed. The Court of Appeals of Maryland held that no constitutionally protected right of privacy existed in the numbers dialed into a telephone. Therefore, use of the pen register did not violate the Fourth Amendment, which guarantees the "right of the people to be secure in their persons, house, papers and effects, against unreasonable searches and seizures."
The Supreme Court held that in determining whether a government-initiated Electronic Surveillance constitutes a "search" within the meaning of the Fourth Amendment, it must determine "whether the person invoking the protection can claim a 'justifiable,' 'reasonable,' or a 'legitimate expectation' of privacy" (Smith). The Court examined the government activity that was being challenged and stated that Smith "could not claim that his property was invaded or that the police intruded into a constitutionally protected area" because the pen register was installed on the telephone company's property. The determination as to whether a "search" took place depended on whether Smith had a "legitimate expectation of privacy" regarding the numbers dialed into his telephone.
In its analysis the Court stated that it is doubtful that people expect privacy in the telephone numbers they dial. People realize that the numbers go through the telephone company once they are dialed, and they also realize that the telephone company keeps records for billing purposes of long-distance numbers dialed. Furthermore, most telephone books inform subscribers that the company has the capacity to "identify to the authorities the origin of unwel-come and troublesome calls." The Court held that Smith probably did not have an expectation of privacy in the telephone numbers he dialed but that even if he did, the expectation was not "legitimate." Therefore, the use of the pen register was not a "search" within the Fourth Amendment, and thus a Search Warrant was not required for its installation.
The dissent in Smith, as well as legal commentators, have expressed concern regarding the holding that there is no legitimate right of privacy in the numbers dialed into the telephone. They assert that there is a reasonable and legitimate expectation of privacy when the numbers are dialed from a person's residence. Justice Potter Stewart, in his dissent, stated that using a telephone within a person's home is private conduct and that, without question, this conduct is entitled to Fourth and Fourteenth Amendment protection.
Although Smith upheld the constitutionality of the installation of a pen register without a warrant, 18 U.S.C.A. § 3123 now requires a court order, based on a law enforcement officer's declaration that the information is relevant to an ongoing investigation, before a pen register may be installed.
Many states have enacted legislation similar to the federal statutes regulating the use of pen registers and trap and trace devices. At the state level, Caller ID and its use of Calling Party Identification has been challenged on several different theories with varying outcomes. Caller ID is a service provided by telephone companies that records each calling party's telephone number, enabling the receiving party to view the number before answering the telephone.
Proponents of Caller ID, primarily telephone companies, believe that it provides additional security to customers because it can detect and prevent obscene and harassing calls and may facilitate emergency response services. The telephone companies also state that customers are able to screen their calls with the service, thus enhancing their privacy.
Opponents of Caller ID argue that the service is an invasion of privacy because some callers may wish to remain anonymous, especially callers with unlisted telephone numbers or users of a confidential crisis hot line. Furthermore, opponents argue that Caller ID is a violation of state and federal trap or trace device statutes.
In determining the legality of Caller ID, states tend to follow either Barasch v. Pennsylvania Public Utility Commission, 133 Pa. Cmwlth. 285, 576 A.2d 79 (1990), affirmed 529 Pa. 523, 605 A.2d 1198 (1992), or Southern Bell Telephone & Telegraph Co. v. Hamm, 306 S.C. 70, 409 S.E.2d 775 (1991). In Barasch the court held that the use of Caller ID was a violation of Pennsylvania's constitutional right of privacy. The court reasoned that people do have a reasonable expectation that the numbers dialed into the telephone are as private as the content of the conversation. In addition, the court held that the Caller ID service violated the state's Wiretapping and Electronic Surveillance Control Act (18 Pa. Cons. Stat. Ann. §§ 5701–5781) (1978) governing the use of trap and trace devices. The statute provides that pen registers and trap and trace devices may not be installed without a court order unless one of the statutory exceptions exists. One of the exceptions provided in section 5771(b)(2) of the act is that if the user of the service consents to the installation of the pen register or trap and trace device, then a court order is not necessary. The Commonwealth Court's decision in Barasch held that because both the calling party and the recipient are users of the service, both must give their consent. The Pennsylvania Supreme Court upheld this part of the Commonwealth Court's holding.
Conversely, in Hamm the court held that Caller ID was not an invasion of privacy because an individual does not have a legitimate expectation of privacy in the numbers dialed into the telephone. Furthermore, although South Carolina has a similar exception to the general prohibition of trap and trace devices, the court held that "user of the service" meant only the subscriber and that therefore consent by the calling party is not necessary. The courts that follow the rationale of Hamm agree that unless indicated otherwise in the statutes, the purpose of trap or trace device statutes is to protect telephone users from unauthorized third-party or government intrusions and not merely to protect users from one another.
Many states have proposed or have already passed legislation authorizing the use of Caller ID. In addition, telephone companies offering Caller ID also offer per-call and per-line blocking to those individuals who wish to remain anonymous. In per-call blocking, a caller may block the transmission of his or her telephone number by dialing a specified code number before dialing. In per-line blocking, the number is blocked on every call unless the caller dials a specified code number to disable the block for a particular call.
Diffie, Whitfield, and Susan Landau. 1999. Privacy on the Line: The Politics of Wiretapping and Encryption. Cambridge, Mass.: MIT Press.
Haglund, Rich. 2003. "Applying Pen Register and Trap and Trace Devices to Internet Communications: As Technology Changes, Is Congress or the Supreme Court Best-Suited to Protect Fourth Amendment Expectations of Privacy?" Vanderbilt Journal of Entertainment Law and Practice 5.
Mason, Geoffrey C. 1996. "Electronic Surveillance." Georgetown Law Journal 84.
Regan, Priscilla M. 1995. Legislating Privacy Technology, Social Values, and Public Policy. Chapel Hill: Univ. of North Carolina Press.
Schultz, Christian David Hammel. 2001. "Unrestricted Federal Agent: 'Carnivore' and the Need to Revise the Pen Register Statute." Notre Dame Law Review 76.
Zitter, Jay M. 1993. "Caller ID System, Allowing Telephone Call Recipient to Ascertain Number of Telephone from Which Call Originated, as Violation of Right to Privacy, Wiretapping Statute, or Similar Protections." American Law Reports 9.