“Trap and trace” sounds like a hidden wire in a lake cabin wall, but Wisconsin law treats it as a narrow kind of communication tracing. It is usually not about hearing a phone call or reading a message. It is about the outside trail of contact. A pen register watches what goes out from a telephone line. A trap-and-trace device watches what comes in. The words stay inside the room, but the tracks near the door can still tell a story.
Wisconsin has its own state rules for pen registers and trap-and-trace devices in Wis. Stat. ss. 968.34 through 968.37. Those sections cover the order requirement, who may apply, what the application must say, when a circuit court may issue an order, how long the order may run, when the order must be sealed, when a provider must help, payment for that help, and the penalty for unauthorized use. Wisconsin also has separate rules for tracking the location of a communications device and for getting stored provider records. Those are related, but they are not the same as a trap-and-trace order.
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What a Pen Register Does
Wisconsin defines a pen register as a device that records or decodes electronic or other impulses that identify the numbers dialed or otherwise sent on the telephone line to which the device is attached. In plain English, it asks: who did this line reach out to?
A pen register should not record the words spoken during a call. It should not read a text message, email, or chat. It follows the outside trail of the communication, not the message itself.
Think of it as someone watching outgoing envelopes at a mail counter. They can see the address and the time the envelope leaves. They cannot open the envelope and read the letter. Still, a stack of envelopes can show habits, repeated contacts, and timing.
What a Trap-and-Trace Device Does
A trap-and-trace device works in the other direction. Wisconsin defines it as a device that captures incoming electronic or other impulses that identify the originating number of an instrument or device from which a wire or electronic communication was sent.
In simple English, it asks: who reached in? It can help identify the origin of incoming communications. Like a pen register, it is not meant to capture what people say or write.
Picture a cabin after fresh snow. A pen register reads tracks leaving the cabin. A trap-and-trace device reads tracks leading toward it. Neither one opens the door and listens to the people inside.
Wisconsin’s Main Statutes
The main Wisconsin pen register and trap-and-trace rules sit in Wis. Stat. ss. 968.34, 968.35, 968.36, and 968.37. The definitions appear in s. 968.27. Those sections are part of the same chapter that covers interception of wire, electronic, and oral communications.
Section 968.34 gives the main restriction and penalty. Section 968.35 covers applications. Section 968.36 covers court orders. Section 968.37 covers help from providers, landlords, custodians, and other people ordered to assist.
Wisconsin also has nearby sections for related tools. Section 968.373 covers warrants to track the location of a communications device. Section 968.375 covers subpoenas and warrants for records or communications held by electronic communication service or remote computing service providers. Those sections can appear in the same investigation, but they are separate roads.
The General Ban in Section 968.34
Wisconsin law says no person may install or use a pen register or trap-and-trace device without first getting a court order under s. 968.36, a federal pen-register order under 18 U.S.C. 3123, or a foreign-intelligence order under 50 U.S.C. 1801 to 1811, unless a listed exception fits.
That phrase “no person” matters. It is not aimed only at police. A private person should not secretly trace another person’s calls or communication traffic because of jealousy, a breakup, a tenant dispute, a workplace fight, or business suspicion.
A knowing violation can bring a fine of up to $10,000, imprisonment for up to nine months, or both. A secret trace can become a legal pit for the person who set it.
Provider Exceptions
Wisconsin gives providers of electronic or wire communication service limited exceptions. A provider may use a pen register or trap-and-trace device for operation, maintenance, and testing of service. A provider may also use one to protect its rights or property, or to protect users from abuse of service or unlawful use of service.
A provider may also record that a wire or electronic communication was started or completed when that helps protect the provider, another provider helping complete the communication, or a user from fraudulent, unlawful, or abusive service use.
User consent is another listed exception. Wisconsin also excludes telephone caller identification service authorized under state utility law. That means ordinary caller ID is not treated the same as a court-ordered trap-and-trace setup.
Ordinary Billing Tools Are Not Pen Registers
Wisconsin’s definition of pen register excludes devices used by a provider or customer for billing, recording as part of billing, cost accounting, or similar business tasks in the ordinary course of business.
That line keeps monthly bills, provider logs, and normal service records from being treated as unlawful pen registers. Phone companies and communication providers need records to run service, bill accounts, prevent fraud, and repair systems.
The difference is purpose and use. A normal billing system is one thing. A hidden tracing tool used to follow another person’s communications is another.
Who May Apply for an Order?
Under Wis. Stat. s. 968.35, the attorney general or a district attorney may apply for an order, or an extension of an order, authorizing or approving installation and use of a pen register or trap-and-trace device.
The application must be in writing and under oath or an equivalent affirmation. It goes to a circuit court for the county where the device is to be located.
The application must identify the person making the application and the law enforcement agency conducting the investigation. It must also include a certification by the applicant that the information likely to be obtained is relevant to an ongoing criminal investigation by that agency.
The Relevance Standard
Wisconsin uses a relevance certification for these orders. The applicant certifies that the information likely to be obtained is relevant to an ongoing criminal investigation.
This is not the same as probable cause. A search warrant often calls for probable cause. A pen-register or trap-and-trace order reaches non-message data, so the state uses a lower gate for this narrow tool.
That lower gate does not make the order limitless. The request must still go through the attorney general or a district attorney. It must be sworn. It must name the agency and investigation. A circuit court must issue the order.
The Circuit Court Order
Under Wis. Stat. s. 968.36, a circuit court issues an ex parte order when the court finds that the application shows the required certification. “Ex parte” means the person tied to the line or account does not appear before the judge during the request.
This is common in criminal investigations because advance notice could warn the subject. The court still acts as the gate, and the order still has boundaries.
The order authorizes installation and use within the jurisdiction of the court. It may also order a provider, landlord, custodian, or other person to give needed help under s. 968.37.
What the Order Must Say
A Wisconsin order must identify, if known, the person to whom the telephone line is leased or in whose name it is listed. It must also identify, if known, the person who is the subject of the criminal investigation.
The order must state the number and, if known, the physical location of the telephone line to which the device will be attached or applied. For a trap-and-trace device, the order must state the geographic limits of the order.
The order must also include a statement of the offense to which the information likely to be obtained relates. This keeps the order tied to a criminal case rather than a broad scan of someone’s phone life.
How Long the Order Can Last
A Wisconsin pen register or trap-and-trace order may run for no more than 60 days. An extension may be granted, but only after a new application and the required court finding.
Each extension may also run for no more than 60 days. One order cannot run forever like a dock light left on through winter. If more time is sought, the state must go back to court.
The dates matter in a real case. A lawyer may compare the application, order, start date, end date, extension papers, provider returns, and agency notes. If data was gathered outside the approved window, that timeline can raise a serious question.
Sealing and Nondisclosure
A Wisconsin order must direct that the order be sealed until the court orders otherwise. The order must also direct the person who owns or leases the line, or who has been ordered to help, not to disclose the pen register, trap-and-trace device, or investigation to the listed subscriber or anyone else unless the court allows it.
This is why a person may not learn about the order while it is active. A provider, landlord, custodian, or other helper may be under a court command to stay silent.
A business that receives such an order should send it to counsel or a trained legal-response person. It should not be passed through casual office messages or discussed with the account holder.
Provider, Landlord, and Custodian Help
Wis. Stat. s. 968.37 says a provider of wire or electronic communication service, landlord, custodian, or other person must furnish information, facilities, and technical assistance when the court order directs that help.
For a pen register, the help must allow installation in an unobtrusive way with minimal service interference. For a trap-and-trace device, the ordered person or provider must install the device on the proper line and furnish added help for installation and operation.
Unless the court orders another method, the results from a trap-and-trace device are furnished to the officer designated by the court at reasonable intervals during regular business hours for the duration of the order.
Payment and Good-Faith Protection
A provider, landlord, custodian, or other person who supplies facilities or technical help must be reasonably paid for reasonable expenses. Wisconsin also blocks lawsuits against providers and specified helpers when they give information, facilities, or assistance according to the court order.
Good-faith reliance on a court order, legislative authorization, or statutory authorization is a complete defense against civil or criminal action under these pen-register and trap-and-trace sections.
That protection works best when the response is narrow. Read the order. Follow the order. Keep a clear record. Do not send extra accounts, extra dates, or message substance outside the signed paper.
How This Differs From Wiretapping
Wisconsin’s wiretap statute, s. 968.31, deals with interception and disclosure of wire, electronic, or oral communications. That is the deeper step. It can involve the words spoken, the message body, or the substance of what people communicate.
A pen register or trap-and-trace device is narrower. It studies numbers, incoming origin, outgoing destination, and signal facts. It should not read the message or record the conversation.
The split is like reading a package label instead of opening the box. Trap-and-trace law studies the label. Wiretap law deals with opening the box.
Wisconsin and One-Party Consent
Wisconsin has a one-party consent rule for many recordings. In general, a person who is a party to a communication, or who has consent from one party, may record that communication unless the recording is done for a criminal or tortious purpose.
That recording rule should not be mixed up with pen registers and trap-and-trace devices. Recording a conversation you are part of is one question. Installing a tool to trace another person’s incoming or outgoing communication traffic is another.
A person can be allowed to record their own conversation and still be barred from secretly tracing someone else’s line, account, phone, router, or communication system.
Tracking a Communications Device Is Separate
Wisconsin has a separate statute for tracking the location of a communications device. Under s. 968.373, a communications device includes any wireless or mobile device that transmits wire or electronic communications.
Except for listed exceptions, an investigative or law enforcement officer may not identify or track the location of a communications device without first getting a warrant. The warrant application must identify the device, known owners or possessors, known investigation subject, the offense, and facts showing probable cause that criminal activity has been, is, or will be in progress and that tracking the device will yield information relevant to an ongoing criminal investigation.
A location warrant may last no more than 60 days. A judge may extend it in 60-day periods if the request still meets the warrant rule. This is a higher gate than the relevance certification used for pen registers and trap-and-trace devices.
Emergency Location Disclosure
Wisconsin allows certain emergency disclosures for device location. The customer or subscriber may consent. A provider may also disclose location information when it believes in good faith that an emergency involving danger of death or serious physical injury exists and the disclosure is relevant to preventing or reducing that danger.
A law enforcement agency may also make a written emergency request in a danger-of-death or serious-injury situation. When location information is disclosed under the emergency paths, the provider must give notice to the customer or subscriber within the time set by the statute.
If criminal evidence was obtained from an emergency disclosure, the law enforcement agency must seek court review within three days. If the judge finds the emergency disclosure was not needed, the judge orders suppression and notice. This shows how Wisconsin treats location data as a separate and more sensitive trail.
Stored Provider Records and Message Content
Wisconsin also has s. 968.375 for records or communications held by electronic communication service or remote computing service providers. A judge may issue a subpoena for subscriber or customer records on probable cause. Those records can include name, address, connection records, session times, service length, service type, subscriber number, network address, and payment information.
A subpoena under that section may not require disclosure of communication content. For content in electronic storage, records that identify device location, or the same subscriber records under a warrant path, a judge may issue a warrant on probable cause.
This is not the same as live pen-register or trap-and-trace use. Stored records look backward at information held by a provider. A pen register or trap-and-trace order watches outside communication data going forward for the order period.
Private People Should Not Try This
A private person should not install hidden software, hardware, router settings, call-forwarding rules, spyware, account filters, or tracing setups to follow someone else’s communications. Suspicion is not enough. A breakup is not enough. A business dispute is not enough. Paying the bill may not be enough.
Do not log into another person’s account to learn who contacted them. Do not hire someone to trace calls or messages outside lawful process. Do not place monitoring equipment on a phone line, router, laptop, office system, shared account, or phone for personal reasons.
Wisconsin’s pen-register statute, wiretap law, computer-crime laws, stalking or harassment laws, workplace rules, family-court orders, civil claims, and federal pen-register law can all enter the room. A hidden trace can turn into a legal pit.
Employers and Business Systems
Employers often keep phone logs, email routing logs, network logs, access records, security alerts, payment records, and fraud records. Some logging may be ordinary business activity when tied to service upkeep, security, billing, fraud control, or abuse response.
But secret tracing of private communications can create risk. Company ownership of a phone, laptop, router, email account, or work system does not answer every question. Written policy, notice, consent, business need, data type, and access limits all matter.
A Wisconsin employer should get legal review before adding systems that trace worker communication patterns beyond ordinary business logging. The safer route is written policy, narrow collection, limited access, and clean records.
Website Tracking and New Data Questions
Pen-register and trap-and-trace ideas began in the phone world, but new disputes can involve websites, apps, analytics scripts, chat boxes, ad pixels, device IDs, IP logs, and account tracking. These systems can send user activity to outside vendors with little visible sign on the screen.
Not every web-tracking dispute is a Wisconsin pen-register case. Some turn on wiretap law, consumer law, contract terms, health data, consent banners, account notices, or how data moves to a vendor.
Wisconsin businesses should review tracking systems before launch. A small script can act like a keyhole if it passes too much user activity to the wrong party.
What Wisconsin Residents Should Know
For Wisconsin residents, the practical point is that the attorney general or a district attorney may seek a circuit court order for a pen register or trap-and-trace device during an ongoing criminal investigation. The target or subscriber may not receive notice while the order is active because sealing and nondisclosure rules apply.
The data may later appear in warrant papers, charging records, discovery, or motion practice. It may show outgoing numbers, incoming origins, timing, or contact patterns. Even without spoken words, that data can carry weight.
If you learn that one of these orders was used in a case involving you, a Wisconsin criminal defense lawyer can review the application, certification, order, dates, extension papers, provider returns, and whether the data stayed inside the court-approved boundary.
What Providers and Businesses Should Do With an Order
A provider, landlord, custodian, platform, or business that receives a Wisconsin order should treat it as legal process. Preserve the document. Limit internal access. Send it to counsel or a trained legal-response person.
Read the order closely. Check the court, date, covered telephone line, physical location if listed, data type, time period, named agency, assistance language, sealing language, and nondisclosure command. Provide what the order requires, not extra data from extra accounts or extra dates.
Keep a clear record of the response. Note when the paper arrived, who reviewed it, what help was given, what data was furnished, and when. A careful response is like tying down a tarp before wind comes off Lake Michigan. It keeps the matter from tearing loose later.
Common Misunderstandings
One common misunderstanding is that trap and trace means listening to calls. It does not. It points to incoming identifying data, not the words spoken.
Another misunderstanding is that Wisconsin uses probable cause for every pen-register order. It does not. The pen-register and trap-and-trace sections use a relevance certification. Device-location warrants and stored provider warrants use probable cause.
A third misunderstanding is that ordinary caller ID is the same as a court-ordered trap-and-trace device. Wisconsin excludes authorized telephone caller identification service from the ban.
A final misunderstanding is that owning an account or paying a bill lets a person trace someone else’s communications. Ownership alone is not a court order, and it may not be consent.
Bottom Line on Wisconsin Trap and Trace Law
Wisconsin trap and trace law sits mainly in Wis. Stat. ss. 968.34 through 968.37, with definitions in s. 968.27. A pen register records or decodes outgoing number data from a telephone line. A trap-and-trace device captures incoming impulses that identify the originating number of the instrument or device that sent the communication.
Wisconsin generally bars installation or use of a pen register or trap-and-trace device without a court order under s. 968.36, a federal order under 18 U.S.C. 3123, or a foreign-intelligence order, unless a provider exception, consent path, or authorized caller ID rule fits. A knowing violation can bring a fine of up to $10,000, imprisonment for up to nine months, or both.
The attorney general or a district attorney may apply in writing under oath to a circuit court for the county where the device is to be located. The application must identify the applicant and law enforcement agency and must certify that the information likely to be obtained is relevant to an ongoing criminal investigation. The order may last no more than 60 days, with 60-day extensions available through the same process. The order must be sealed and must include nondisclosure language.
Providers, landlords, custodians, and other ordered helpers must give technical help with minimal service interference when the court directs it. They must be reasonably paid and receive protection for compliant help. Location tracking of wireless or mobile devices is handled under s. 968.373 and generally needs a warrant. Stored provider records and communication content are handled under s. 968.375. The law does not open the letter, but it can study the envelope. In Wisconsin, that envelope has its own court gate.