Surveillance is what most people think a PI does — and it is, in fact, the backbone of many investigations. But the legal landscape around surveillance is narrower and more technical than it looks on television. Get it wrong and the evidence is inadmissible, the client is exposed, and the investigator loses their license. Get it right and the same evidence becomes decisive in family court, civil litigation, or criminal defense.
The Basic Rule: Public Space Is Fair Game
A licensed PI can lawfully observe and photograph any person in a public place where that person has no reasonable expectation of privacy. That includes streets, parking lots, public parks, restaurants, and the exterior of most commercial buildings. The Cornell Legal Information Institute has a plain-language explanation of how courts define the expectation of privacy.
Where the Line Moves: California-Specific Rules
Two-Party Consent for Audio Recording
California is a two-party consent state. Under Penal Code Section 632, you generally cannot record a confidential communication without the consent of all parties. That means an investigator who captures video of a subject in public may be prohibited from also capturing the audio of a confidential conversation happening at the same table. Getting this wrong is a criminal offense — not merely a civil issue.
GPS Tracking
California Vehicle Code Section 637.7 prohibits attaching an electronic tracking device to a vehicle without the consent of the registered owner. There are narrow exceptions — most notably for the vehicle's registered owner tracking their own property — but a PI hired to track a spouse's car generally cannot attach a GPS device without the vehicle owner's permission.
Trespass and Curtilage
Investigators cannot enter private property to conduct surveillance without permission. The curtilage — the fenced or otherwise-protected area immediately surrounding a home — is entitled to the same privacy protection as the interior. A photograph of the front door from the sidewalk is legal; a photograph of the same door from three feet inside the property line is not.
Peeping and Video Voyeurism
Any recording that captures a person in a state of undress, in a place where they have a reasonable expectation of privacy, is a serious criminal offense. This applies to windows, hotel rooms, changing areas, and any interior space visible only through invasive means.
Why the Rules Matter for Your Case
Evidence collected illegally is not just useless — it can poison the entire case. Judges routinely exclude improperly obtained evidence and, in some cases, the offending party is exposed to counterclaims for invasion of privacy or unlawful recording. A licensed investigator who knows the rules keeps you on the right side of the courthouse.
What Compliant Surveillance Looks Like in Practice
- Video captured from public streets, sidewalks, or lawful vantage points
- Photographs of subjects in public spaces without their consent (public activity is not private)
- Public-records research — court files, business filings, real property records, licensing agencies
- Publicly visible social media activity
- Consensual interviews of witnesses who agree to speak
- Corroboration between physical surveillance and open-source intelligence
What a Reputable PI Will Refuse to Do
- 1Attach a GPS device to a vehicle they do not own or have permission to track
- 2Break into an email, social media, or cloud account
- 3Record confidential audio without all-party consent
- 4Enter private property, including backyards, hallways of apartment buildings, or hotel rooms
- 5Impersonate a law enforcement officer or government agent
Why Working With a Licensed PI Protects You
A client is often the person most exposed if surveillance goes wrong. Amateur efforts, DIY tracking devices, or a friend-of-a-friend who "used to be a cop" can create liability that dwarfs the value of any evidence obtained. Working with a licensed investigator means the evidence is defensible and the method is not the story. See our guidelines and investigations pages for more on how we structure engagements.
Bottom Line
Surveillance done right wins cases. Surveillance done wrong loses cases and creates new ones. The difference is a licensed professional who knows exactly where the legal lines are and works comfortably within them.
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