Is It Legal to Spy on Someone's Phone?

Disclaimer: This post is educational and does not constitute legal advice. Laws vary by jurisdiction and change over time. Consult a licensed attorney for guidance specific to your situation.

Let's start with the answer nobody wants to hear: in most scenarios where someone is asking "can I legally monitor this person's phone?": the answer is no. The question is reasonable enough. The law in the United States (and most Western jurisdictions) has made covert surveillance without consent a serious criminal offense, regardless of your relationship to the target. Marriage doesn't help you. Paying someone's phone bill doesn't help you. Being their parent when they're 19 doesn't help you.

What's remarkable about electronic surveillance law is how consistently it has rejected common-sense arguments about implied consent in relationships. Courts have heard virtually every version of "but she's my wife" and "I own his phone", and rejected them. Federal prosecutors have charged spouses, employers, private investigators, and parents under statutes whose maximums reach ten years.

This isn't theoretical. Real people go to federal prison for this. Real civil judgments are handed down with $100,000+ verdicts. Understanding exactly where the lines are (and why they're drawn there), is the difference between lawful oversight and a federal felony.

The Three Federal Statutes That Govern Electronic Surveillance

Three overlapping federal laws create the backbone of US surveillance law. Violating any one of them generates criminal exposure. Violating all three simultaneously (which many surveillance scenarios do) multiplies your criminal counts accordingly.

The Wiretap Act: 18 U.S.C. § 2511

The Electronic Communications Privacy Act of 1986 substantially updated the Omnibus Crime Control and Safe Streets Act of 1968, producing the modern Wiretap Act. Section 2511 prohibits any person from intentionally intercepting any wire, oral, or electronic communication. The word "intercepting" means capturing the communication while it's in transit: a phone call in progress, an SMS being sent, internet traffic flowing across a connection.

The federal baseline is one-party consent: if you are a participant to the communication being recorded, you can legally record it. A telephone conversation you are personally having can be recorded without telling the other party (under federal law (states vary dramatically on this). If you are not a participant), if you are a hidden third party listening in: you need the consent of at least one participant to avoid liability.

Penalties under § 2511: imprisonment of up to 5 years per violation, plus civil damages. The civil provision (18 U.S.C. § 2520) is a private right of action that allows the victim to sue for the greater of actual damages or $10,000 per violation, plus attorney's fees. Each intercepted communication can be a separate violation. An abusive partner who runs a stalkerware app for 30 days intercepts potentially hundreds of separate communications: each potentially a separate $10,000 civil violation.

In re Pharmatrak, Inc. Privacy Litigation (1st Cir. 2003) is instructive: the court found that a web analytics company intercepting communications without proper consent violated the Wiretap Act even where parties had technically consented to some data collection. The courts interpret "interception" broadly.

The Stored Communications Act: 18 U.S.C. § 2701

The Stored Communications Act, enacted as Title II of ECPA, governs access to electronic communications stored on third-party systems, email sitting in an inbox, iMessages stored in an iCloud account, text message logs at a carrier, cloud backup files. The Wiretap Act handles real-time interception; the SCA handles stored data.

Under § 2701, intentionally accessing without authorization (or exceeding authorized access to) a facility through which electronic communication services are provided, in order to obtain stored communications, is a federal offense.

This statute is what makes logging into your spouse's Gmail account a federal crime. You are accessing a facility (Google's servers) without authorization. The fact that you know the password (perhaps because you once watched them type it, or because it's saved on a shared device) does not constitute authorization in the legal sense. Authorization requires the account holder's consent.

Criminal penalties under § 2701(b) turn on purpose. Where the offense is committed for commercial advantage, malicious destruction or damage, private commercial gain, or in furtherance of any criminal or tortious act, the maximum is 5 years for a first offense and 10 years for a subsequent one. In every other case the maximum is 1 year for a first offense and 5 years for a later one. A jealous spouse acting out of suspicion rather than gain usually sits in the lower tier, and the civil exposure is the larger number in that scenario.

Epstein v. Epstein (7th Cir. 2016) shows the shape of these disputes: during an acrimonious divorce a wife placed an auto-forwarding rule on her husband's email accounts so his messages copied to her. The Seventh Circuit held that the allegation stated a claim under the federal Wiretap Act and reinstated it, observing that Congress probably did not anticipate the statute being used as a tactical weapon in a divorce. Divorce attorneys who advise clients to access their spouse's accounts to gather evidence routinely expose both the client and themselves to professional consequences.

The Computer Fraud and Abuse Act: 18 U.S.C. § 1030

The CFAA was enacted in 1986 primarily to prosecute computer hackers. Smartphones are computers. Installing monitoring software on a phone without authorization, accessing someone else's device to retrieve their communications, or remotely accessing a device through malware: these are CFAA violations.

The CFAA has been the basis for some of the most notable surveillance prosecutions. In United States v. Drew (C.D. Cal. 2009), the court wrestled with how the CFAA applies to social engineering and unauthorized access. In Van Buren v. United States (2021), the Supreme Court narrowed the "exceeds authorized access" standard to a gates-up-or-down question: a person exceeds authorized access by obtaining information in areas of a system that are off limits to them, and improper motive alone does not make a CFAA violation out of information they were entitled to obtain.

The practical implication: an employer who has authorization to access company systems does not thereby have authorization to access an employee's personal files on those systems. A parent who owns a device does not automatically have authorization to install covert monitoring software against the adult child's will.

Penalties: up to 10 years for first offenses under certain aggravating circumstances, with higher penalties for repeat offenses or offenses causing serious damage.

Spouse and Partner Surveillance: Where Most People Get This Wrong

This is the category that generates the most prosecutions, the most civil lawsuits, and the most questions. People in troubled relationships, divorce proceedings, or custody disputes routinely seek ways to monitor their partners, and routinely expose themselves to serious criminal and civil liability in the process.

The "I Own the Phone" Argument

Some partners try to justify covert monitoring by pointing out that they pay for the phone or the phone plan. This argument fails legally for a straightforward reason: ownership of hardware does not grant unlimited access rights to the data stored on it or transmitted by it. The CFAA analysis focuses on authorization, not ownership. The SCA analysis focuses on the account holder's consent, not who paid for the service.

Courts have applied the same reasoning to shared computers for decades: letting someone else use a machine you own does not amount to consent to have their activity on it recorded. The same logic carries over to a phone on a family plan.

The "Implied Consent in Marriage" Theory

This one has been tried repeatedly and rejected every time. The argument goes: by virtue of marriage, spouses have an implied mutual consent to access each other's private information. Courts have treated this argument with skepticism bordering on contempt.

The reason is simple: if implied marital consent were a defense to wiretapping charges, it would effectively make domestic surveillance legal, creating a class of persons (married partners) whose communications have no legal protection from their spouse. Congress deliberately chose not to create this exception. Federal courts have honored that legislative choice.

The "I Was Worried About Them" Defense

Also not a defense. Neither the Wiretap Act, the SCA, nor the CFAA contain mental state exceptions for well-intentioned surveillance. Good intentions reduce your sentence; they don't eliminate your conviction.

What Stalkerware Prosecution Looks Like in Practice

FTC v. Retina-X Studios (October 2019) was the FTC's first case against a stalkerware developer. Retina-X and its owner sold three monitoring apps (MobileSpy, PhoneSheriff, and TeenShield) marketed for watching children and employees, and the settlement barred them from selling monitoring products unless the app requires the device user to be told the device is being monitored. The company was also ordered to destroy the data it had already collected.

Selling the software can itself be the crime. In United States v. Akbar (E.D. Va. 2014), the chief executive behind the StealthGenie app pleaded guilty to sale and advertisement of an interception device, was sentenced to time served, fined $500,000, and ordered to forfeit the source code. The Justice Department described it as the first criminal conviction for advertising and selling a mobile spyware app.

For the person who installs it rather than sells it, the exposure runs through the three federal statutes above plus state eavesdropping and stalking law, and where the target is a former partner, the federal cyberstalking statute (18 U.S.C. § 2261A) is available on top.

Evidence Obtained Through Illegal Surveillance Is Generally Inadmissible

Divorce attorneys see this play out regularly: a client, convinced their spouse is cheating, installs a stalkerware app or records phone conversations without consent. They obtain evidence of exactly what they suspected. The other spouse's attorney then moves to exclude the evidence as illegally obtained, and often wins, because the evidence was obtained in violation of federal law.

The victimized spouse then brings a counterclaim for civil damages under § 2520. The surveilling spouse is now defending against civil damages, potentially facing criminal referral, AND has no usable evidence. This is a factual scenario that plays out in family courts regularly.

Parental Monitoring of Minor Children: Broad But Not Unlimited

Parents occupy a privileged legal position with respect to monitoring their minor children. The legal framework here derives from two sources: parental consent doctrine (a parent can consent to certain actions on behalf of a minor child, including monitoring) and the ownership/authorization logic (if you own the device and the account, you have authorization to access it).

This gives parents considerably more latitude than any other monitoring relationship, but it's not unlimited, and it does not survive the child's 18th birthday.

What Federal Law Generally Permits for Minor Children

• Installing parental control software (Google Family Link, Apple Screen Time, Bark, Qustodio, Net Nanny) on devices owned by the parent
• Reviewing the minor child's text messages, emails, social media activity, and browsing history
• Using carrier-level family tracking features (Verizon Smart Family, T-Mobile FamilyMode and the equivalents) on accounts you manage
• Enabling location sharing through platform features on accounts you control
• Recording conversations to which you are a party (one-party consent covers this)

The legal basis is straightforward: the parent owns the device, controls the account, and can consent to monitoring on the minor's behalf. This covers all three federal statutes simultaneously.

The Age Gray Zone

Federal law doesn't specify at what age parental monitoring authority begins to fade: that's left to common law, state law, and the courts. The general principle is that as children develop a reasonable expectation of privacy, covert surveillance becomes harder to justify legally and ethically.

Courts in several states have found that covertly monitoring a 16 or 17-year-old's private communications is treated differently than monitoring a 10-year-old. Pollock v. Pollock (6th Cir. 1998) is the case that set the terms. A mother tape-recorded calls between her 14-year-old daughter and the girl's father and stepmother because she believed the child was being emotionally abused. The Sixth Circuit recognized a vicarious consent exemption to the federal wiretap statute: a parent may consent on a minor child's behalf where the parent has a good faith, objectively reasonable basis for believing the recording is necessary for the child's welfare. The court then found the mother's motives genuinely in dispute and sent the case back for trial, which is the point worth carrying: the doctrine turns on a fact question about the parent's reasons, and a court can send it to a jury. Good faith is also not a complete defense when the monitoring becomes a pretext for something else (controlling an older teenager's relationships, for instance).

The Magic Cutoff: Age 18

Once a child turns 18, parental monitoring authority ends completely. A 19-year-old on your phone plan has exactly the same legal protections as any other adult. Monitoring their communications without their informed, affirmative consent exposes you to the same federal liability as monitoring a complete stranger.

This is not hypothetical. Parents have faced legal action for continuing to monitor adult children's devices, particularly in the context of controlling family dynamics where the "parenting" extends well past the age of majority.

The College Student Problem

Many parents continue to pay for their college student's phone and phone plan. Payment for service does not substitute for consent. If your 20-year-old is on your family plan and you install monitoring software on their phone without their knowledge, you are committing a federal offense. Period.

Employer Monitoring: Broad Permission, Important Limits

Employee monitoring is the area where legal permission is most explicit, but the limits are less understood than most employers assume.

What the Law Generally Permits

Employers can monitor activity on company-owned devices and company networks provided employees have been notified. The notice requirement is critical, monitoring without prior disclosure is legally riskier even when the monitoring itself would otherwise be permissible.

The standard framework:

• Company equipment: Monitoring is strongly defensible on company-owned devices, company email accounts, and company network traffic. You own the device; you set the terms.
• Company networks: Traffic on your business network (even from employee-owned devices) can be monitored with notice.
• Business purpose: Monitoring must serve a legitimate business purpose: productivity measurement, security incident detection, regulatory compliance, IP protection.
• Written notice: Employment agreements and acceptable use policies should explicitly state that monitoring may occur and what it encompasses.

States With Stricter Requirements

Several states have enacted laws that go beyond federal minimums:

Connecticut (Conn. Gen. Stat. § 31-48d): Employers must provide prior written notice to employees before engaging in any electronic monitoring, including monitoring of email, internet use, or telephone communications.

Delaware (19 Del. C. § 705): Similar to Connecticut, written notice of the types of monitoring, the means of monitoring, and the frequency required.

New York (Civil Rights Law § 52-c): In force since 7 May 2022, private employers who monitor or intercept telephone conversations, email, or internet usage must give written notice at the time of hiring, obtain the employee's written or electronic acknowledgment, and post the monitoring notice somewhere employees will see it. Civil penalties run $500 for a first violation, $1,000 for a second, and $3,000 for each one after that.

California: The state constitution's privacy provisions give California employees stronger baseline protections. Monitoring must still satisfy a legitimate business purpose test, and the scope must be proportional to that purpose. Courts have found that monitoring of personal communications on company devices can violate employee privacy rights in some circumstances.

What Employers Cannot Do

• Monitor employees' personal devices used for personal purposes off company time (even if the same device is used for work)
• Monitor personal email accounts accessed from company devices when employees have a reasonable expectation of privacy in those accounts
• Use monitoring as pretext for discriminatory action
• Monitor union organizing activities (which may trigger NLRA analysis in addition to wiretapping statutes)
• Monitor employees' home networks or personal internet use outside work hours without explicit contractual authorization

GPS Tracking of Employees

Tracking company vehicles during work hours: broadly legal with notice. Tracking employees' personal vehicles at any time: not legal without consent. Tracking company vehicles outside work hours: legally contested: some courts have found this unreasonable absent specific business justification.

The line is clearest in the following formulation: monitoring activity that occurs on company time, company equipment, and company premises is defensible with notice. Monitoring that extends into employees' personal lives: their personal devices, their personal vehicles, their personal locations outside work hours, requires explicit contractual consent and even then may fail proportionality analysis in some jurisdictions.

GPS Tracking Laws: Stricter Than You Think

AirTags, Tile trackers, Brickhouse GPS units, and similar devices have become the surveillance tools of choice for jealous partners, suspicious parents, and private investigators. The law has moved aggressively to restrict covert GPS tracking.

The Fourth Amendment Foundation

United States v. Jones (2012) established the constitutional baseline: law enforcement attaching a GPS tracker to a vehicle without a warrant and monitoring it for 28 days constitutes an unreasonable search under the Fourth Amendment. While this constrains government actors, it established a framework that courts have applied when analyzing private GPS tracking conduct.

Carpenter v. United States (2018) extended this principle to historical cell-site location data, with Chief Justice Roberts writing that the "seismic shifts in digital technology" require reconsidering how Fourth Amendment principles apply. The decision's reasoning: that sustained, comprehensive location tracking is categorically different from isolated surveillance, has influenced how courts analyze private stalking claims as well.

State-by-State Prohibitions

The commonly repeated figure of "more than 25 states" overstates how many have a statute written for this. The National Conference of State Legislatures counts roughly fifteen. Nine of them (Delaware, Illinois, Michigan, Oregon, Rhode Island, Tennessee, Texas, Utah and Wisconsin) prohibit installing a location tracking device on a motor vehicle without the owner's consent. A further group (California, Florida, Hawaii, Louisiana, Minnesota, New Hampshire and Virginia) reaches further, prohibiting the use of an electronic tracking device to determine a person's location regardless of whether a vehicle is involved.

That does not make covert tracking lawful in the remaining states. It means the charge comes from stalking, harassment or electronic surveillance law instead, where the penalty tier is often higher than the dedicated tracking statutes carry.

California Penal Code § 637.7: No person or entity may use an electronic tracking device to determine the location or movement of a person. The statute has two exceptions on its face: the registered owner, lessor or lessee of the vehicle consenting to the device, and lawful use by a law enforcement agency. There is no parental exception written into it, and a violation is a misdemeanor with no felony escalation in the section itself. Conduct that also amounts to stalking is charged separately under Penal Code § 646.9, which does carry felony exposure.

Texas Penal Code § 16.06: Knowingly installing a tracking device on a motor vehicle owned or leased by another person without their consent is a Class A misdemeanor (up to one year in jail, $4,000 fine). Effective consent of the owner or lessee is an affirmative defense, so a spouse is covered only where the vehicle is theirs or the owner agreed, never by the marriage alone.

Illinois (720 ILCS 5/21-2.5): The electronic tracking provision sits in the property offenses chapter, prohibits using an electronic tracking device to determine the location or movement of a person, and is a Class A misdemeanor. Consent of the registered owner, lessor or lessee is an exception. Illinois eavesdropping, a different offense under 720 ILCS 5/14-2, is the Class 4 felony.

AirTag Stalking: A Growing Enforcement Category

Apple introduced AirTag in April 2021. The devices are small enough to be placed in a bag, jacket pocket, or wheel well, and they ride on Apple's Find My network, which Apple describes as a crowdsourced network of over one billion devices, to report location without any infrastructure of the tracker's own.

The scale of the misuse was documented early. Motherboard obtained police records mentioning AirTags across an eight-month period from eight US police departments: of about 150 reports, 50 were women contacting police after an unwanted-tracking notification or after hearing an AirTag chime, and in 25 of those the woman could name a man in her life, an ex-partner, a husband, a boss, whom she suspected of planting it. That report is a sample of eight departments rather than a national count, so it establishes the pattern rather than its total size.

Two things follow for a reader. The unwanted-tracking notification is the mechanism that surfaces most of these cases, and it works only for a tracker that is separated from its owner and travelling with you. And the charge that lands is usually a stalking or protective-order offense in state court, because the dedicated tracking statutes described above cover only part of the country.

Two-Party (All-Party) Consent States: A Critical Distinction

Federal law sets a floor of one-party consent for recording conversations. Eleven states are squarely stricter, requiring every party to consent before any party may record a phone call, and recording without that consent is a state offense even where you are a participant. A further group is mixed, and being precise about which is which matters, because the popular "thirteen two-party states" lists disagree with each other about exactly those borderline states.

The eleven clearly all-party states:

The mixed states, where the answer depends on the facts:

• Connecticut (Conn. Gen. Stat. § 52-570d): all-party for telephone recording as a matter of civil liability, with the criminal eavesdropping statute reading as one-party. Treat it as all-party.
• Michigan (Mich. Comp. Laws § 750.539c): the statute reads all-party and carries up to 2 years and a $2,000 fine, but the Michigan Court of Appeals held in Sullivan v. Gray (1982) that the offense covers "the private discourse of others" and so excludes recording by a participant. The Michigan Supreme Court has not settled it.
• Oregon (Or. Rev. Stat. § 165.540): one-party for telephone calls, all-party for in-person conversations.
• Nevada sits on the list because the state courts have read NRS 200.620 as requiring all parties to consent to a telephone recording, rather than because the statute says so plainly.

The practical implication is significant: a person in Florida who records a phone call without the other party's knowledge has committed a felony even if that person is their own spouse, and even if they themselves are a participant in the conversation.

California's statute has particular bite. In Kearney v. Salomon Smith Barney (Cal. 2006), the California Supreme Court held that California's all-party consent law applies when a California resident is a party to a recorded call, even if the recording occurs in a one-party consent state. Cross-state recording disputes frequently default to the stricter state's law.

Interstate Call Recording

When a call crosses state lines, there's a conflict-of-laws question. The general rule that courts have applied: if any party to the call is in an all-party consent state, apply that state's law. This means that if you're in Texas (one-party consent) and you record a call with a California resident without telling them, you may have violated California Penal Code § 632.

International Surveillance Laws: A Brief Survey

European Union: GDPR and Criminal Law

The General Data Protection Regulation (GDPR) applies to processing personal data of EU residents. Personal data includes location data, communications content, and any information about an identifiable individual. Covert monitoring without a lawful basis violates GDPR, which is processed separately from any criminal liability under member state law.

GDPR penalties can reach 4% of global annual turnover or €20 million, whichever is higher. These penalties apply to organizations: the more relevant exposure for individual private surveillance is criminal liability under member state law.

Germany's StGB (Strafgesetzbuch) § 202a-202c criminalizes unauthorized interception of data with up to 3 years imprisonment. France's Penal Code Article 226-1 makes it a crime to intentionally intercept, use, or disclose private communications without consent, up to 1 year imprisonment and €45,000 fine.

For employers monitoring EU employees: the GDPR requires a lawful basis (usually legitimate interests), prior notice to employees, a Data Protection Impact Assessment for high-risk monitoring, and often consultation with works councils or employee representatives. The proportionality principle means monitoring must be limited to what is strictly necessary for the stated business purpose.

United Kingdom

Post-Brexit, the UK operates under UK GDPR and the Data Protection Act 2018 alongside its pre-existing surveillance statutes.

Computer Misuse Act 1990 criminalizes unauthorized access to computer material (Section 1), unauthorized access with intent to commit further offenses (Section 2), and unauthorized modification of computer material (Section 3). Penalties up to 10 years imprisonment. Accessing a partner's phone or email without consent falls squarely within Section 1.

Investigatory Powers Act 2016 (the "Snoopers' Charter") governs bulk surveillance by government agencies but also establishes that private individuals cannot intercept communications. The Regulation of Investigatory Powers Act 2000 (RIPA) remains in force for certain interception scenarios.

Stalking and protection orders: The Protection from Harassment Act 1997, as amended by the Protection of Freedoms Act 2012, specifically prohibits conduct including electronic monitoring that amounts to stalking. This has been used to prosecute covert surveillance by intimate partners even where the specific technology-crime nexus was less clear.

Canada

Criminal Code of Canada Section 184 prohibits the interception of private communications. One-party consent is a defense, if a party to the communication consents, no offense. Employer monitoring of employee communications on company equipment is generally permitted with notice.

PIPEDA (Personal Information Protection and Electronic Documents Act) governs how private organizations collect, use, and disclose personal information. Employer monitoring of employees must satisfy PIPEDA's purposes and consent requirements. Several provincial privacy laws (PIPA in Alberta and BC, Quebec's Law 25) impose stricter requirements.

Provincial stalking and criminal harassment laws (Criminal Code § 264) have been applied to covert GPS tracking and sustained electronic surveillance of intimate partners.

The Consequences: What Actually Happens When Surveillance Is Discovered

Criminal Prosecution Scenarios

The following scenarios have all resulted in federal criminal charges in the United States:

Stalkerware installation by intimate partners: Multiple federal CFAA prosecutions. In several cases, the defendant also faced state cyberstalking charges and domestic violence charges simultaneously. Federal sentences have ranged from probation (first offense, cooperation) to 3-5 years imprisonment.

Exceeding authorized access: the CFAA is narrower here than employers often assume. In United States v. Nosal (9th Cir. 2012, en banc), the Ninth Circuit held that "exceeds authorized access" reaches restrictions on obtaining information and not restrictions on using it, so an employee who is entitled to see a record does not commit a CFAA offense by looking at it for a forbidden purpose. The Supreme Court took the same view in Van Buren. What still bites is reaching into a place you were never given access to, which is exactly what installing monitoring software on someone else's phone does.

Account access during divorce proceedings: Civil cases are far more common than criminal prosecutions in this scenario, but referrals to US Attorneys for criminal prosecution do occur, particularly when the surveillance was extensive or the victim was harmed.

Civil Judgment Exposure

The Wiretap Act's civil provision (18 U.S.C. § 2520) allows the victim to recover:

• The greater of actual damages or $10,000 per violation
• Punitive damages in appropriate cases
• Reasonable attorney's fees

Each intercepted communication is a separate violation. A stalkerware app running for 90 days can intercept thousands of separate communications, texts, emails, calls. Even if the court awards only $10,000 per violation and limits the count to 20 violations, that's $200,000 in statutory damages plus fees. Civil judgments in wiretapping cases have reached into the hundreds of thousands and, in extreme cases, the millions.

Luis v. Zang (6th Cir. 2016) shows how far the civil exposure reaches. A husband secretly installed WebWatcher on his wife's computer. The plaintiff was Javier Luis, a man in Florida who had been corresponding with her and whose messages were captured along with hers. The Sixth Circuit reversed the dismissal and held that the software vendor itself could face Wiretap Act liability, because the program routed communications to the vendor's own servers as they were written, including drafts that were never sent, which the court treated as near real-time interception rather than access to stored data. Two lessons for anyone considering a monitoring app: the people on the other end of the conversations are potential plaintiffs too, and the vendor's involvement does not put the installer at arm's length from the interception.

Protective Orders and Custody Consequences

Courts have recognized covert surveillance (particularly stalkerware installation) as a manifestation of domestic abuse. The discovery of monitoring software is frequently cited as grounds for emergency protective orders. Family courts in custody disputes treat surveillance as evidence of controlling behavior, which weighs heavily against the surveilling parent in custody determinations.

In multiple reported cases, the party who installed stalkerware to gain tactical advantage in a divorce lost primary custody precisely because the installation was treated as evidence of coercive control.

Decision Framework: Before You Touch That Phone

Use this decision tree before taking any action involving monitoring another person's device or communications:

Do you own this device AND does the person using it have no reasonable
expectation of privacy in it (e.g., company device with clear monitoring notice)?
  YES → Monitoring may be permissible. Confirm notice requirements met.
  NO → Continue ↓

Is the person a minor child in your legal custody?
  YES → Transparent parental controls likely permissible. Age matters.
  NO → Continue ↓

Do you have the person's explicit, informed, affirmative consent to monitoring?
  YES → Monitoring with consent is generally permissible. Document the consent.
  NO → STOP. You are in federal felony territory.

No relationship status (marriage, partnership, family) substitutes for a "yes" in that tree. If you cannot check one of those three boxes, the monitoring is illegal under federal law and likely illegal under state law as well.

The Bottom Line

Surveillance law in the United States is built around one organizing principle: consent. Not relationship, not ownership, not good intentions. Consent.

Monitoring with the subject's explicit knowledge and agreement is generally defensible. Monitoring covertly is where criminal and civil liability begins, regardless of how sympathetic your reasons, regardless of how troubled the relationship, regardless of what you suspected or feared.

The practical consequence is that many of the surveillance scenarios people assume are normal or legal, checking a spouse's text messages, installing a tracker on a partner's car, logging into an ex's email, are federal crimes. Not minor infractions. Federal crimes whose maximums run from one year to ten.

If you are facing a situation where you feel you need to monitor someone (a child's safety, a suspected unfaithful partner, an employee you don't trust) the appropriate steps are:

1. Consult a licensed attorney in your jurisdiction before taking any action
2. Understand that courts have consistently rejected "I had good reasons" as a defense
3. Consider transparent alternatives: location sharing apps that both parties use knowingly, explicit consent agreements, professional help for relationship issues
4. Recognize that illegally obtained evidence generally cannot be used for the purposes you intended it for

The law does not distinguish between the jealous spouse and the controlling abuser in its treatment of covert surveillance. Both are committing the same federal offense.