Texas Pen Register & Trap and Trace Device Offenses — Penal Code § 16.03

The controlling statute

Chapter 16 of the Texas Penal Code criminalizes electronic surveillance in layers. Section 16.03 sits between the wiretap statute (§ 16.02) and the stored-communications statute (§ 16.04), and it targets one specific tool: the pen register and its mirror image, the trap and trace device. The offense is defined in a single sentence.

“A person commits an offense if the person knowingly installs or uses a pen register or trap and trace device to record or decode electronic or other impulses for the purpose of identifying telephone numbers dialed or otherwise transmitted on a telephone line.” — Tex. Penal Code § 16.03(a)

A pen register records the outgoing dialing, routing, addressing, or signaling information of a communication — classically, the numbers dialed from a target phone. A trap and trace device does the reverse, capturing the originating numbers of calls coming in. The Texas definitions live in Article 18B.001 of the Code of Criminal Procedure, which § 16.03(b) incorporates by reference; the same subsection borrows the definition of “communication common carrier” from Article 18A.001. The critical limit is baked into the definition: these devices capture the fact and routing of a communication, not its contents.

Section 16.03 does not outlaw the devices themselves — it outlaws their unauthorized installation and use. Texas gives law enforcement a lawful path: a peace officer or prosecutor may apply for a court order authorizing a pen register or trap and trace device under Chapter 18B of the Code of Criminal Procedure. What § 16.03 punishes is the person who skips that process — a private actor, an investigator, or an officer acting without a valid order — and knowingly uses the technology to harvest another person’s dialing data off a phone line.

Metadata, Not Content: How Is § 16.03 Different from Wiretapping?

The line that separates § 16.03 from the offenses on our wiretapping and tracking-device page is the line between metadata and content. A pen register answers who called whom, and when. A wiretap answers what was said. Texas grades those very differently.

Under § 16.02, intercepting the contents of a wire, oral, or electronic communication — listening to a call, reading a text or email in transit — is a second-degree felony, carrying two to twenty years. Under § 16.06, secretly installing a GPS tracker on someone’s vehicle is a Class A misdemeanor. Section 16.03 occupies the middle: capturing the dialing and routing data — the non-content metadata — is a state jail felony. The federal system draws the same map, regulating pen registers and trap and trace devices under a distinct statute (18 U.S.C. §§ 3121–3127) with a much lower threshold than the federal Wiretap Act.

This distinction is not academic. It decides which statute the State can charge, what the prosecution has to prove, and how strong a suppression motion is. It is also where charging errors happen: a phone-monitoring app that captures message text is a § 16.02 or § 16.04 problem, not a § 16.03 problem, and a device that only logs numbers is the reverse. Pinning the State to the correct statute — and its correct elements — is often the first move in one of these cases.

Classification & punishment range

Section 16.03(d) sets the grade in three words: the offense “is a state jail felony.” There is no tiered ladder inside § 16.03 itself — the base grade is fixed. What can move the exposure is the general enhancement machinery in Chapter 12 that applies to every state jail felony, summarized below.

Two features of state jail felonies matter to a § 16.03 case. First, a straight state jail sentence is served day-for-day — there is no parole and limited good-time credit — so even a low number carries real weight. Second, § 12.44 lets a court, and in some cases the State, treat a state jail felony as a Class A misdemeanor for punishment or final judgment, a route that can keep a first-time, low-harm surveillance case out of felony territory altogether. Which door a case goes through is a negotiation, and it starts on day one.

Elements the State must prove

Every element must be proved beyond a reasonable doubt. Section 16.03 is a short statute, but each word is a place the State can fall short:

1. A culpable mental state — “knowingly”

The accused must have knowingly installed or used the device. A person who plugs in equipment without understanding what it captures, or who is handed a phone with monitoring already running, has a genuine mental-state defense. The statute does not reach negligent or accidental capture of routing data.

2. Installation or use of a pen register or trap and trace device

The item must actually meet the Article 18B.001 definition — a device or process that records or decodes dialing, routing, addressing, or signaling information. If the tool captures message contents, it is not a pen register, and the wrong statute has been charged. If it captures nothing that identifies a number, it is not covered at all.

3. Purpose of identifying numbers dialed or transmitted

The use must be for the purpose of identifying telephone numbers dialed or otherwise transmitted on a telephone line. This is a specific-purpose element. Equipment used to test a line, protect a network, or diagnose a fault — not to identify who a person is calling — falls outside the target of the statute.

4. Absence of authorization

Chapter 18B of the Code of Criminal Procedure authorizes court-ordered pen registers. A person acting under a valid order — or within one of the § 16.03(c) defenses below — has not committed the offense. Where the State’s own actor relied on a defective order, the authorization question can cut in the defendant’s favor.

The Statute’s Built-In Defenses

Section 16.03(c) writes three affirmative defenses directly into the offense. These are not arguments a court might entertain — they are statutory, and if the evidence raises one, the jury must be instructed on it. Each targets a category of legitimate line activity that would otherwise sweep in innocent conduct.

Communication common carriers

An officer, employee, or agent of a communication common carrier who installs or uses the equipment to record numbers in the normal course of business — to protect the carrier’s property or services, or to assist a person the actor reasonably believes is a peace officer authorized under Chapter 18B — has a defense. Phone companies log dialing data every day for billing and fraud control.

Lawful enterprises protecting their own service

An officer, employee, or agent of a lawful enterprise may use the equipment where doing so is a necessary incident to rendering its service or protecting its property — provided the use is not to gather information for a law enforcement or private investigative agency, other than information about the theft of the enterprise’s own communication or information services.

Persons authorized under Chapter 18B

A person authorized to install or use a pen register or trap and trace device under Chapter 18B of the Code of Criminal Procedure — the officers and agents acting under a valid court order — is expressly protected. The defense turns on the validity and scope of the order, which is exactly where a suppression fight often begins.

How Texas & Federal Courts Have Interpreted § 16.03

Because prosecutions under § 16.03 itself are uncommon, the governing law comes from the constitutional and statutory cases about pen registers — and here Texas has taken a notably more protective path than federal law. The four decisions below frame every pen-register case in this state.

Pen registers capture routing data, not contents. The United States Supreme Court drew the content/metadata line decades ago. In United States v. New York Telephone Co., 434 U.S. 159 (1977), the Court held that pen registers are not governed by the federal Wiretap Act because they “do not ‘intercept’ . . . they do not acquire the ‘contents’ of communications” — the devices “do not hear sound” and “disclose only the telephone numbers that have been dialed.”^[1] That holding is the doctrinal spine of § 16.03: Texas created a separate device statute precisely because dialing data is a different thing from conversation, and it is the reason a monitoring tool that grabs message text belongs under a different section.

Federally, pen-register use is not a “search.” Two years later, in Smith v. Maryland, 442 U.S. 735 (1979), the Supreme Court held that installing and using a pen register “was not a ‘search,’ and no warrant was required,” because a caller “voluntarily convey[s]” dialed numbers to the phone company and so has no legitimate expectation of privacy in them.^[2] Smith is the origin of the “third-party doctrine.” It still controls the federal Fourth Amendment analysis — but, as the next case shows, it does not control Texas.

Texas rejects the third-party doctrine for dialed numbers. This is the point that matters most to a Texas defendant. In Richardson v. State, 865 S.W.2d 944 (Tex. Crim. App. 1993), the Texas Court of Criminal Appeals declined to follow Smith under the state constitution, holding that “the use of a pen register may well constitute a ‘search’ under Article I, § 9 of the Texas Constitution” because “society recognizes as objectively reasonable the expectation of the telephone customer that the numbers he dials . . . will not be published to the rest of the world.”^[3] The court noted that the pen-register statute “does not require an applicant show probable cause,” and remanded to decide whether a court-ordered pen register without probable cause is “unreasonable” under the Texas Constitution. For the defense, Richardson is a live tool: in Texas, a state actor’s pen-register data may be attacked on state-constitutional grounds that federal law forecloses.

The doctrine is narrowing, not expanding. Most recently, in Carpenter v. United States, 585 U.S. 296 (2018), the Supreme Court declined to extend Smith’s third-party doctrine to cell-site location information, holding that acquiring that comprehensive record is a Fourth Amendment search requiring a warrant.^[4] Carpenter preserved Smith for old-fashioned dialed numbers but signaled that courts will scrutinize modern surveillance that reveals far more than a list of digits — an argument that grows sharper as “pen register” technology captures richer routing and signaling data than a 1979 device ever could.

Defense strategies

L and L Law Group builds § 16.03 defenses on the statute’s narrow elements and on the surveillance law that surrounds them. Common theories include:

• Wrong statute charged. If the tool captured message contents rather than dialing data, the conduct is not § 16.03. Forcing the State to prove the device meets the pen-register definition can move a case out of — or into — a completely different grade. See our interception and tracking-device page.
• No “knowingly.” The mental-state element is real. A person who did not know what the equipment captured, or who inherited a running configuration, did not knowingly use a pen register.
• Not for the prohibited purpose. Line testing, network protection, and diagnostics are not use “for the purpose of identifying telephone numbers.” The specific-purpose element is contestable on the facts.
• Statutory defense applies. The three § 16.03(c) defenses — carrier, lawful enterprise, and Chapter 18B authorization — are jury issues once raised by the evidence.
• Texas-constitutional suppression. Where the data came from a state actor, Richardson supports a motion to suppress under Article I, § 9 and Article 38.23 that has no federal counterpart. A defective or overbroad Chapter 18B order is the classic target.
• Attribution and authentication. Who installed the device, on whose line, at whose direction — all of it must be proved, and digital-evidence chains are frequently incomplete.

For the broader playbook — suppression practice, pretrial diversion, and grade reduction — see our criminal defense strategies hub and our guide to Texas punishment ranges.

What Happens After a Surveillance-Device Arrest in Collin, Dallas, Denton, or Tarrant County?

A § 16.03 charge usually surfaces inside a larger investigation — a stalking or family-violence file, a business-dispute case, or a computer-crimes matter where digital forensics turned up a monitoring setup. Because it is a felony, the case proceeds by arrest, magistration (the Article 15.17 appearance where bond and conditions are set), and indictment by a grand jury, followed by pretrial settings and either resolution or trial. When the surveillance targeted a partner or ex-partner, expect no-contact conditions and possibly a protective order layered on top of the charge.

Where the case is heard depends on the county. Collin County felonies — including Frisco arrests — run through the district courts at the Collin County Courthouse (the Russell A. Steindam Courts Building) in McKinney. Dallas County cases proceed at the Frank Crowley Courts Building, Denton County cases at the Denton County Courts Building, and Tarrant County cases at the Tim Curry Criminal Justice Center in Fort Worth. Our office defends surveillance-device cases in all four from Frisco, and the first work is usually technical: pinning the State to the correct statute, testing the Chapter 18B authorization, and evaluating a Texas-constitutional suppression motion under Richardson before the case ever reaches a plea posture.