Yes. It is legal to hire a licensed private investigator to follow and observe someone in Massachusetts and New Hampshire — as long as the surveillance happens in places open to public view and the investigator stays inside the law. Watching someone’s movements on public streets, in parking lots, or in businesses is lawful. Secretly recording their conversations, placing a tracker on their car without consent, or entering private property is not. Here’s where the line actually sits.
What a Licensed Investigator Can Legally Do
- Follow and observe in public. Streets, sidewalks, parking lots, restaurants, stores, parks — anywhere a person has no reasonable expectation of privacy.
- Photograph and video record from a public vantage point. If it can be seen from where the public is allowed to be, it can generally be documented.
- Document vehicles, locations, times, and interactions. This is the core of a surveillance report.
- Research public records — court filings, property records, business registrations — and use professional investigative databases.
- Interview people who are willing to talk. Witnesses, neighbors, associates.
What an Investigator Cannot Do — In Either State
- Secretly record conversations. Both Massachusetts and New Hampshire are “all-party consent” states for recording private conversations. Massachusetts’ wiretap statute (M.G.L. c. 272, § 99) is among the strictest in the country; New Hampshire’s is RSA 570-A. Recording a conversation without everyone’s consent is a crime, and the recording is useless as evidence anyway.
- Trespass. No entering homes, yards, garages, or other private property. No filming through windows into a home.
- Place a GPS tracker on a vehicle the client doesn’t own. Without the owner’s consent or a court order, it’s off limits. (See the FAQ below.)
- Hack accounts or phones. Accessing someone’s email, social media, or device without authorization is a federal and state crime.
- Impersonate police or use “pretexting” to obtain protected records such as phone or financial records.
- Harass or intimidate. Surveillance has to be covert and non-confrontational. Conduct that makes the subject aware they’re being followed and causes fear can cross into criminal harassment or stalking under state law.
A professional investigator refuses these shortcuts not just because they’re illegal — but because evidence gathered that way gets thrown out and can expose you, the client, to liability.
Why “Licensed” Matters
Both states license private investigators — Massachusetts through the State Police, New Hampshire through the Department of Safety. A license means the investigator is bonded, vetted, and accountable. It also matters jurisdictionally: an investigator licensed only in New Hampshire cannot legally conduct surveillance in Massachusetts, and vice versa. For anyone near the border — Salem, Nashua, Lowell, Lawrence, Haverhill — a dual-licensed investigator means the case doesn’t stop at the state line. See the areas we cover.
Is the Evidence Usable in Court?
Evidence gathered lawfully by a licensed investigator — timestamped photos and video, written surveillance logs, a report with documented chain of custody — is admissible in New Hampshire Family Division and Superior Court and in Massachusetts Probate & Family, Superior, and District Courts. Investigators can be called to testify. This is why the “how” matters as much as the “what.” How our surveillance operations work.
Common Reasons People Hire a PI to Follow Someone
- Suspected infidelity in a marriage or divorce — cheating spouse investigations
- Concerns about a co-parent’s conduct during custody time — custody investigations
- Workers’ comp or disability claims that don’t match a claimant’s activity
- Cohabitation that affects alimony
- Employee misconduct on company time
This article is general information, not legal advice. Laws change and facts matter; for your specific situation, talk to an attorney licensed in your state.
Frequently Asked Questions
Can a private investigator put a GPS tracker on my spouse’s car in Massachusetts?
Only with the vehicle owner’s consent or a court order. If the car is jointly owned, the legal picture is murkier and you should ask an attorney first. Most professional investigators avoid trackers entirely and use lawful mobile surveillance instead — it produces better, more defensible evidence.
Can a PI record a conversation if they’re part of it?
Not without the other parties’ consent in Massachusetts or New Hampshire — both require all parties to agree. This is different from some other states. A licensed investigator in MA or NH will not record private conversations covertly.
Is it stalking if a PI follows someone?
Lawful, covert surveillance by a licensed investigator for a legitimate purpose is not stalking. Stalking and criminal harassment laws target conduct that is intended to, or does, cause fear or distress — repeated confrontation, intimidation, threats. Professional surveillance is designed so the subject never knows it happened.
Do I need a lawyer before hiring a private investigator?
No — individuals hire investigators directly all the time. But if your case is headed to court, involving your attorney early helps: the investigator can tailor the report to what the court needs, and some attorneys prefer to retain the investigator themselves. We regularly work both ways.
Donahue Investigative Services & Executive Protection — Salem, NH. Licensed in New Hampshire (#M-2025-0424) and Massachusetts (#LP1599A). Led by a former Salem, NH police officer with 34 years in law enforcement.
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