1. When Is a Trap and Trace Order Required?
Penal Code § 638.51 generally prohibits a person from installing or using a pen register or trap and trace device without authorization under §§ 638.52 or 638.53. The restriction also reaches private entities, while specified exceptions permit communications providers to conduct legitimate service-related activities.
Information Covered by the Statute
Section 638.50 distinguishes outgoing from incoming communication data. A pen register records dialing, routing, addressing, or signaling information, while a trap and trace device captures incoming information identifying a communication's source.
Neither definition includes communication content. Identifying a caller differs from recording a conversation, which raises separate interception requirements.
Exceptions for Communications Providers
Section 638.51(b) permits providers to use these devices for specified purposes:
- Operating, maintaining, or testing communication services.
- Defending provider rights or property.
- Addressing abusive or unlawful service use.
- Recording communication activity to address specified fraudulent or abusive use.
- Acting with the service user's consent.
These exceptions do not create unrestricted surveillance authority. Businesses using website tracking technologies must also consider whether their tools meet the statutory definitions.
2. Court Order Requirements under Penal Code § 638.52
A peace officer submits a written application under oath or equivalent affirmation to a magistrate. The application identifies the officer, investigating agency, relevant offense, and anticipated information's relevance to an ongoing criminal investigation.
Investigative Relevance and Probable Cause
The magistrate must find probable cause that the device will lead to information or evidence within a category listed in § 638.52(b). An officer's certification of investigative relevance alone does not satisfy this additional requirement.
Qualifying grounds include stolen property, evidence of specified criminal conduct, and information assisting in locating certain individuals. The statute also identifies certain child-exploitation offenses and other designated violations.
The application must connect the expected information to an applicable ground rather than rely on a general investigative interest.
Required Terms and Location Limits
An order identifies the subscriber and investigation subject when known, the relevant line, and the offense under investigation. A trap and trace order also specifies applicable geographic limits.
Under § 638.52(c), information obtained solely through this authority cannot disclose a subscriber's physical location beyond what the telephone number reveals. More precise location collection requires a separate legal basis.
Duration and Extensions
An initial order authorizes collection for no more than 60 days. Each extension requires a new application and continued probable cause, with another 60-day maximum.
Section 638.52(g) also requires sealing during the order's effective period, including extensions. The order imposes specified nondisclosure obligations concerning the device and investigation.
3. Emergency Authorization and Filing Deadlines
Section 638.53 permits oral judicial approval before a written application when narrow emergency conditions exist. Investigators still need a magistrate's authorization and grounds supporting an ordinary order.
Grounds for Immediate Approval
The magistrate must find probable cause of an emergency connected to a criminal investigation. The circumstances must also establish substantial danger to life or limb justifying immediate installation before ordinary approval can be obtained.
An approaching investigative deadline alone does not satisfy these conditions.
The Second Full Court Day Deadline
The officer must submit a written application to the approving magistrate by midnight of the second full court day after installation. A subsequently issued order records the oral approval time and applies retroactively.
Without an authorizing order, use ends when the requested information is obtained, the application is denied, or the statutory deadline arrives, whichever occurs first.
4. Communications Carrier Duties and Compensation
Section 638.52 imposes technical assistance duties when an order directs them. Pen register and trap and trace provisions differ, so the authorization's wording determines the required assistance.
Assistance and Reasonable Expenses
Designated providers and other persons must furnish the information, facilities, and technical assistance required by an applicable order. Trap and trace provisions also address installation and operation at an authorized officer's request.
Assistance must minimize interference with affected services. The requesting law enforcement agency must reasonably compensate qualifying persons for reasonable expenses.
These requirements affect operational decisions involving communications law.
Scope and Good-Faith Reliance
The identified line, collection period, and technical directions help determine whether requested assistance falls within an order. A demand extending beyond those terms raises a separate compliance question.
Section 638.51(d) provides a complete defense to specified civil or criminal actions for good-faith reliance on a qualifying order or emergency authorization. It does not independently authorize collection outside applicable legal process.
Related issues arise under electronic surveillance laws.
5. Subscriber Notice and Delayed Disclosure
Penal Code § 638.54 establishes notice duties separate from investigative confidentiality. The government generally must notify identified targets after authorization ends unless a court permits delay.
The 30-Day Notice Rule
The government generally must notify identified targets within 30 days after an order, extensions, or emergency request terminates. Notice describes the investigation with reasonable specificity and includes the order or an explanation of emergency grounds.
Before that deadline, the government can request delayed notification through a sworn affidavit. A court can authorize a delay of up to 90 days upon the required adverse-result finding, with qualifying extensions available.
Notice after Delay and DOJ Reporting
After an approved delay expires, the government generally has three days to notify identified targets. The notice includes additional information about records obtained and the grounds for delay.
If no target was identified when authorization was issued, the agency instead submits the required report to the Department of Justice. The ordinary deadline is three days after authorization ends, subject to statutory delay provisions.
The department publishes reports within 90 days of receipt and may redact identifying information.
6. Legal Challenges and State-Federal Differences
Collection without valid authorization can raise criminal, evidentiary, and compliance questions. The available response depends on the violation, the affected person, and the legal process involved.
Penalties and Available Remedies
Violating § 638.51 can result in a fine of up to $2,500, imprisonment under statutory alternatives, or both.
Section 638.55(a) permits suppression motions concerning information obtained or retained in violation of the Fourth Amendment or the chapter. Subdivision (c) separately allows qualifying targets and recipients of defective process to petition the issuing court for modification, invalidation, or destruction of unlawfully obtained information.
The Attorney General may also bring a civil action to compel government compliance.
Federal Law Uses a Different Standard
Federal procedures appear in 18 U.S.C. §§ 3121–3127. Federal orders generally rely on certification that the requested information is relevant to an ongoing criminal investigation.
California's statutory process additionally requires probable cause tied to enumerated grounds. The issuing authority and applicable jurisdiction determine which requirements govern.
Restrictions on Certain Out-of-State Requests
Section 638.52(m) prohibits orders intended to investigate or obtain evidence of defined prohibited violations involving abortion lawful under state law. Penal Code § 1546.5 separately restricts certain communications companies from assisting specified out-of-state investigations.
These restrictions depend on the company's statutory status, the legal process, and the investigation's purpose. They do not prohibit unrelated lawful requests.
Businesses evaluating such demands may encounter additional telecommunications law obligations.
16 Oct, 2026
