Surveillance of Telephone Communications


When you’re speaking on the telephone, you have a reasonable expectation of privacy—unless there’s someone standing near enough to overhear. To listen to your phone conversations secretly, law enforcement agents need a wiretap warrant. Wiretap warrants have rather strict requirements. The officers:

    1.  must show probable cause that a specific crime has been or 
         is being committed;

    2.  must list names of specific person(s) to be overheard;

    3.  must give detailed descriptions of subjects to be overheard;

    4.  must stop listening within 30 days (or seek a 30-day 
         extension);

    5.  must include provisions for terminating the wiretap; and

    6.  must report to the judge concerning intercepted 
         conversations.

Wiretap warrants are more trouble for the police to obtain and report on than regular search warrants, so they’re less commonly used. By contrast, law enforcement agents frequently employ a “pen register” and/or “trap and trace device.” A pen register is a list of the telephone numbers of outgoing calls from a particular phone line. A trap and trace device collects the phone numbers of incoming calls to a particular line. Both types of surveillance collect the time and length of the calls, as well. To utilize a pen register or trap and trace device, the police just need a court order, which they get by showing that the information derived would be relevant to an ongoing criminal investigation.

For an important case, the officers will still want a wiretap, since it reveals the actual conversations, while a pen register or trap and trace device just provides a list of phone numbers.

Note that law enforcement agents can obtain voice mail with a regular search warrant—they don’t need a wiretap warrant. Many people prefer to use an answering machine, rather than a voice mail service, because it provides more control over the privacy of stored messages.

There are two situations in which investigating officers can legally listen to and record your phone conversations without getting a wiretap warrant

    • calls from a prisoner in a jail, prison or immigration detention 
      facility (including calls from a prisoner to a lawyer)

    • calls to or from an undercover officer or an informant.

Sometimes, while on the phone, people speculate or make jokes about the line being tapped. This is a poor idea, since acknowledging that someone may be listening means that you don’t have a reasonable expectation of privacy. If you’re on the phone and someone does make a stupid comment about the line being tapped, say: “That’s a silly joke. I believe that I have a reasonable expectation of privacy in this phone conversation.”

There are certainly instances in which law enforcement agents listen to phone conversations illegally. Such unlawful activities may not come to light if the officers are clever in laundering the information they’ve obtained, for example, attributing it to a confidential informant. It’s easier for law enforcement to listen illegally to a cordless phone or a cell phone, than to a corded phone (the kind that has a curly cord running from the receiver to the phone itself).


1.  Although many telephones are advertised as being particularly secure against eavesdropping, surveillance technology is improving all the time.  The system that ensures privacy today may not do so tomorrow.  In the end, the most private conversations are those that are conducted while walking around outdoors - assuming the person you're talking to isn't an undercover officer or an informant.