“Trap and trace” sounds like a hidden wire in a motel wall, but Texas law treats it as a narrower kind of communication tracing. It is usually not about hearing a phone call or reading a message. It is about the outer trail of contact. A pen register looks at what goes out. A trap-and-trace device looks at what comes in. The words stay inside the room, but the marks outside the door can still tell a story.
Texas handles this area mainly through Chapter 18B of the Code of Criminal Procedure and Section 16.03 of the Penal Code. Chapter 18B covers applications, court orders, emergency use, mobile tracking devices, stored customer data, location information, provider duties, policies, audits, and remedies. Penal Code Section 16.03 creates a crime for unlawful use of a pen register or trap-and-trace device. Together, those laws draw the line between lawful court-supervised tracing and private or unauthorized snooping.
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What a Pen Register Does
A pen register is a tool used to record or decode outgoing phone or communication signals. In plain English, it asks: who did this line or device reach out to? The old image is a phone line and numbers dialed from that line. Modern cases may involve phones, wireless systems, electronic communication services, and related equipment.
A pen register is not supposed to capture the conversation itself. It should not hear the words spoken in a call. It should not read the body of a text, email, or chat. It studies the outside path, not the message inside.
Think of it as someone watching outgoing envelopes at a mail counter. They can see the address and the time the envelope leaves. They do not open the envelope and read the letter. Still, a stack of envelopes can show patterns, routines, and ties between people.
What a Trap-and-Trace Device Does
A trap-and-trace device works in the other direction. It asks: who reached in? It is used to identify the origin of incoming communications to a line, device, account, or service. In the old phone setting, it could help identify the number that called the target line.
Like a pen register, a trap-and-trace device should not capture message content. It traces the incoming path. It does not open the call or message and look inside.
Picture a ranch gate after a rain. A pen register reads tire tracks leaving the gate. A trap-and-trace device reads tire tracks heading toward it. Neither one walks into the house and listens at the table.
Texas Uses Chapter 18B
Texas Code of Criminal Procedure Chapter 18B is the main procedure chapter for these tools. Its title covers installation and use of tracking equipment and access to communications. That chapter is broader than old pen-register law. It includes pen registers, trap-and-trace devices, ESN readers, similar equipment, mobile tracking devices, location information, and stored electronic customer data.
The chapter starts with definitions, including “authorized peace officer,” “electronic communications service,” “electronic customer data,” and other terms. The definition of authorized peace officer includes sheriffs, constables, municipal police, certain state officers, prosecutor investigators, Texas Alcoholic Beverage Commission agents, Parks and Wildlife officers, attorney general investigators, certain inspector general officers, arson investigators, school peace officers, and insurance investigators.
Texas also uses the term “designated law enforcement office or agency.” That term matters because some pen-register and trap-and-trace powers in Chapter 18B are tied to the Department of Public Safety or certain large local agencies and inspector general offices.
Application Requirements
Under Chapter 18B, an application for an order authorizing a pen register, ESN reader, trap-and-trace device, or similar equipment must be made in writing under oath. It must include the subscriber’s name and the telephone number and location of the communication device, to the extent that information is known or can reasonably be found.
The application must also state that installing and using the device or equipment will likely produce information material to an ongoing criminal investigation. That is the Texas gate for this part of Chapter 18B.
This is not a private request. It is a sworn court process tied to law enforcement work. A person cannot skip the judge because tracing sounds useful. The court paper is the line between lawful investigation and unlawful snooping.
Who May Ask for the Order?
Chapter 18B uses a prosecutor-centered filing path in many situations, with requests from authorized peace officers. The application goes to a judge with proper jurisdiction under the chapter. The law does not turn every officer, employee, or private investigator into a person who may install tracing equipment on their own.
In practice, the application should identify the line or device, the known subscriber information, the agency, and the ongoing criminal investigation. The sworn statement gives the judge a record to review.
The judge acts as the gate. The officer or prosecutor brings the request. The court decides whether the order may issue. That gate may be narrower or wider depending on the kind of data or device, but Chapter 18B keeps the request in court-supervised territory.
Orders for Pen Registers and ESN Readers
Article 18B.101 allows a judge, on presentation of a proper application, to order installation and use of a pen register, ESN reader, or similar equipment. The order is for use by an authorized peace officer commissioned by the Department of Public Safety or an authorized peace officer of a designated law enforcement office or agency.
At the applicant’s request, the judge must direct a communication common carrier or electronic communications service provider to give information, facilities, and technical help needed to support the installation and use. The work must be done in a way that is unobtrusive and causes as little service interference as possible.
An ESN reader is related but not identical to a pen register. It can concern identifying information from communication devices. Texas groups it with pen-register-type equipment in this subchapter, so the same court-order theme runs through it.
Orders for Trap-and-Trace Devices
Article 18B.102 covers trap-and-trace devices or similar equipment. On presentation of a proper application, a judge may order installation and use of a trap-and-trace device or similar equipment on the proper line by a communication common carrier or another person.
The judge may direct the carrier, landlord, custodian, or other person to provide information, facilities, and technical help needed to install or use the device. The work must be done unobtrusively and with minimal interference to service.
Unless the court orders another method, the results from the device or equipment are given to the applicant named by the court at reasonable intervals during regular business hours while the order remains in effect.
How Long a Texas Order Lasts
An order for installation and use under this part of Chapter 18B may last no more than 60 days. Texas calculates that period from the earlier of the date the device or equipment is installed or the 10th day after the order is entered.
A prosecutor may seek an extension before the order expires. Each extension may not exceed 60 days. There is one longer path: with the consent of the subscriber or customer of the service on which the device or equipment is used, the court may extend an order for up to one year.
Those dates matter. A lawyer may compare the order date, installation date, 10-day trigger, expiration date, extension papers, provider returns, and agency reports. If data was gathered beyond the allowed window, the timeline can become a real fight.
Sealing the Application and Order
A district court must seal an application and order granted under Chapter 18B. That means the person tied to the line or device may not learn about it while the order is active.
Sealing is not a casual office preference. It is part of the legal design. An open file could warn the subject of the investigation and defeat the point of the tracing tool.
Businesses, carriers, landlords, custodians, and service providers should treat a sealed order with care. It should go to counsel or a trained legal-response team. It should not be copied widely inside the company or discussed with the customer.
Carrier and Service Provider Compensation
Chapter 18B says a communication common carrier or electronic communications service provider that gives facilities and assistance under a pen-register or similar-equipment order is entitled to compensation at prevailing rates.
A communication common carrier that gives facilities and assistance under a trap-and-trace order also receives compensation at prevailing rates. That payment rule recognizes that legal compliance can take staff time, engineering work, records work, and system access.
The order is not a favor. It is legal process. The provider should do what the order requires, keep a clean record, and avoid producing extra data outside the paper signed by the judge.
Emergency Use
Texas also has an emergency path in Chapter 18B. Article 18B.151 allows emergency installation and use of a pen register or trap-and-trace device when a peace officer reasonably believes that an immediate life-threatening situation exists, that installation is required before an order can be obtained with due diligence, and that sufficient grounds exist to obtain an order.
This emergency path is narrow. It is built for fast danger, not routine speed. A case feeling urgent is not the same as a life-threatening situation.
After emergency installation, Texas requires a quick follow-up order. If the officer does not apply for or does not obtain court authorization, Texas limits the use of the information in criminal proceedings. That keeps emergency use tied to court review rather than letting it float free.
Evidence From Emergency Use
Chapter 18B includes an admissibility rule for emergency use. If an authorized peace officer does not apply for or does not obtain authorization for the emergency pen register or trap-and-trace device, the state may not use information gained through that device as evidence in a criminal proceeding.
That rule gives the emergency path teeth. It is not enough to say the situation felt urgent. The officer must follow the statute and get the court involved.
For defense lawyers, emergency papers deserve close review. The questions are when the device started, what danger was claimed, when the application was filed, whether the order was granted, and what data the state later tried to use.
Penal Code Section 16.03
Texas Penal Code Section 16.03 creates the crime of unlawful use of a pen register or trap-and-trace device. A person commits the offense if the person knowingly installs or uses such a device to record or decode electronic or other impulses for the purpose of identifying telephone numbers dialed or otherwise transmitted on a telephone line.
The offense is a state jail felony. That can mean serious criminal exposure, including jail time, a fine, a felony record, and the long shadow that follows a felony charge.
This is the warning for private people. A hidden trace is not just “checking the bill.” It can become a felony case if it fits the statute and no defense applies.
Affirmative Defenses Under Section 16.03
Texas gives several affirmative defenses to prosecution under Penal Code Section 16.03. One covers an officer, employee, or agent of a communication common carrier who installs or uses equipment in the normal course of business to protect carrier property or services, or to assist someone reasonably believed to be an authorized peace officer under Chapter 18B.
Another covers an officer, employee, or agent of a lawful enterprise who uses equipment while engaged in activity that is needed for service or for protection of the enterprise’s property or services, as long as the activity is not done to gather information for law enforcement or a private investigative agency, except information tied to theft of communication or information services.
The third covers a person authorized to install or use a pen register or trap-and-trace device under Chapter 18B. These defenses are narrow. They do not give private people a loose permission slip to trace communications for personal reasons.
How This Differs From Wiretapping
Wiretapping deals with content. Texas Penal Code Section 16.02 and Code of Criminal Procedure Chapter 18A cover interception of wire, oral, and electronic communications. That is the deeper step: hearing, recording, or capturing what people actually say or write.
A pen register or trap-and-trace device should deal with outside signal and number data. It should not hear the call. It should not read the message body. It should show contact direction, not conversation substance.
The split is like reading a package label instead of opening the box. Chapter 18B studies the label. Chapter 18A and Penal Code wiretap rules deal with opening the box.
Mobile Tracking Devices Are Different
Chapter 18B also has a separate subchapter for mobile tracking devices. A mobile tracking device is not the same as a pen register or trap-and-trace device. A tracking device follows movement. A pen register or trap-and-trace device follows communication traffic.
Texas requires a separate order for installation and use of a mobile tracking device. The application must be written, signed, and sworn. It must identify the person, vehicle, container, item, or object to be tracked and must lay out the facts supporting the request.
The distinction matters. A contact trail is not a travel trail. A phone can create both, but Texas law gives them different lanes.
Location Information Held in Electronic Storage
Texas also has separate rules for certain location information held in electronic storage. Chapter 18B contains a warrant requirement for covered stored location information. It also includes rules on issuance, duration, sealing, emergency disclosure, and limits on evidence use.
Location information can be more revealing than a simple contact record. It can show where a device has been or where it is believed to be. That is closer to a map of movement than a list of calls.
Do not treat a pen-register order, trap-and-trace order, mobile-tracking order, and stored-location warrant as the same paper. They answer different questions and call for different legal steps.
Stored Electronic Customer Data
Chapter 18B also covers government access to stored electronic customer data. That category can include customer identity information, use records, recipient or destination data, contents of wire or electronic communications, stored data, and location information held by a provider.
Stored customer data is different from live pen-register or trap-and-trace use. One asks for records or data held by a provider. The other watches signals going forward under an order.
Texas has court-order and warrant paths for stored data, plus notice, backup preservation, subpoenas, preclusion of notification, provider disclosure limits, reimbursement, and remedies. A real case should match the request to the right Chapter 18B subchapter.
Policies, Authorized Officers, and Audits
Texas adds internal controls for law enforcement offices and agencies that use pen registers, ESN readers, trap-and-trace devices, or similar equipment. A designated law enforcement office or agency must adopt a written policy and submit it for approval by the Department of Public Safety.
Only named authorized officers may possess, install, operate, or monitor the equipment after approval. The department may audit a designated office or agency to check compliance. Chapter 18B also requires reporting of certain expenditures.
Those controls matter because tracing tools can be powerful even without message content. Texas does not leave them as loose gear in an evidence room. The agency must have policy, approved names, and oversight.
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.
Texas Penal Code Section 16.03, Texas wiretap law, federal pen-register law, computer-crime rules, stalking and harassment laws, workplace rules, family-court orders, and civil claims can all come into play. A secret trace can become a legal pit.
Employers and Business Systems
Employers often keep phone logs, email routing logs, access records, network logs, security alerts, payment records, and fraud records. Some logging may be ordinary business activity when tied to service upkeep, cybersecurity, 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 Texas 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 newer 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 Texas 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.
Texas 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 Texas Residents Should Know
For Texas residents, the practical point is that law enforcement may seek a Chapter 18B order for live non-content tracing during an ongoing criminal investigation. The person tied to the line or device may not receive notice while the order is active because the application and order are sealed.
The data may later appear in warrant papers, charging records, discovery, or motion practice. It may show outgoing contacts, incoming origins, timing, device identifiers, or similar contact data. Even without spoken words, that data can carry force.
If you learn that one of these orders was used in a case involving you, a Texas criminal defense lawyer can review the application, order, timing, extension papers, provider returns, emergency claim if any, policy compliance, and whether the data stayed inside the court-approved boundary.
What Providers and Businesses Should Do With an Order
A carrier, electronic communications service provider, landlord, custodian, platform, or business that receives a Texas 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 phone or device, physical location if listed, data type, time period, named applicant, assistance language, sealing language, and return instructions. Produce what the order requires, not extra data from extra accounts or extra dates.
Keep a clean 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 gate before a West Texas wind. It keeps the matter from swinging 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 private people can trace calls if they own the account or pay the bill. Texas Penal Code Section 16.03 makes unauthorized use a state jail felony unless a defense applies.
A third misunderstanding is that a Chapter 18B order and a mobile-tracking order are the same thing. They are not. One traces communication traffic. The other tracks movement.
A final misunderstanding is that a 60-day order starts whenever the agency feels ready. Texas ties the period to the earlier of installation or the 10th day after the order is entered.
Bottom Line on Texas Trap and Trace Law
Texas trap and trace law centers on Code of Criminal Procedure Chapter 18B and Penal Code Section 16.03. Chapter 18B creates the court-order process for pen registers, ESN readers, trap-and-trace devices, similar equipment, mobile tracking devices, stored customer data, and location information. Penal Code Section 16.03 creates a state jail felony for unlawful use of a pen register or trap-and-trace device.
A Chapter 18B application for a pen register, ESN reader, trap-and-trace device, or similar equipment must be in writing and under oath. It must give known or reasonably available subscriber, number, and device-location information. It must state that the installation and use will likely produce information material to an ongoing criminal investigation.
A judge may order installation and use of a pen register, ESN reader, trap-and-trace device, or similar equipment. The order may require a carrier, provider, landlord, custodian, or other person to provide information, facilities, and technical help with minimal service interference. Results from a trap-and-trace device are usually furnished to the applicant at reasonable intervals during regular business hours.
The order may run no more than 60 days from the earlier of installation or the 10th day after entry. Extensions may run no more than 60 days, except that a one-year extension is possible with the customer or subscriber’s consent. The application and order are sealed. Emergency use exists for life-threatening situations, but court review must follow. The law does not open the letter, but it can study the envelope. In Texas, that envelope is wrapped in Chapter 18B procedure and a felony warning for unauthorized use.