Private investigator evidence is admissible in a New Hampshire divorce when it was gathered lawfully, in places open to public view, and can be authenticated by the investigator who collected it. Family Division judges routinely accept timestamped surveillance video, photographs, written surveillance logs, and the investigator’s own testimony. What they throw out is evidence obtained by trespassing, secret recording, or breaking into a spouse’s accounts.
This guide explains how that evidence actually gets used in a New Hampshire divorce, where it carries weight, and the mistakes that get it excluded. It is written from the investigator’s side of the table. It is not legal advice, and your attorney decides what to file and when.
Where PI evidence matters in a New Hampshire divorce
New Hampshire divorces are heard in the Circuit Court, Family Division. Most are filed on no-fault grounds (irreconcilable differences), but New Hampshire still allows fault grounds under RSA 458:7, and adultery is one of them. That distinction matters because investigator evidence can affect four separate parts of a case:
- Grounds. If a spouse files on fault grounds such as adultery, the court needs proof. Documented surveillance is how that proof is usually built.
- Property division. New Hampshire’s property-division statute lets a judge consider fault when it caused the breakdown of the marriage and either substantial physical or mental suffering or substantial economic loss to the marital estate. Evidence that marital money was spent on an affair falls squarely here.
- Parenting rights and responsibilities. Custody in New Hampshire is decided on the best interests of the child. A judge wants to know how each parent actually behaves when they think no one is watching: who is around the children, whether the parenting schedule is followed, and whether there is drinking, drug use, or reckless driving with kids in the car.
- Support. A spouse who claims they cannot work but is seen working for cash, or who claims a modest lifestyle while spending freely, is a credibility problem for the judge to weigh. Surveillance documents it.
Most of the family cases we work out of Salem, NH land in the Rockingham and Hillsborough County Family Division courts, and the same evidence standards apply across the state.
What judges accept: the evidence that holds up
A judge is asking three questions about anything an investigator brings in. Is it relevant? Is it authentic? Was it obtained legally? Evidence that clears all three is routinely admitted. The forms that hold up best:
- Timestamped video and photographs taken from public property or places open to the public: streets, parking lots, restaurants, hotel entrances, a front yard visible from the road. The investigator testifies to when and where each clip was shot and that it has not been altered.
- A contemporaneous surveillance log. A running record of times, locations, vehicles, plate numbers, and observed activity, written during the surveillance rather than reconstructed later. It corroborates the video and fills the gaps between clips.
- A written investigative report that states what was observed, in order, without speculation. Judges notice the difference between “subject entered the residence at 11:42 p.m. and exited at 6:15 a.m.” and “subject spent the night with his girlfriend.” The first is evidence. The second is a conclusion the judge will draw on their own.
- Public-record findings. Property records, business filings, court records, and licensed-database results that document assets, addresses, or relationships. These are often the quiet backbone of a financial case.
- The investigator’s testimony. A licensed investigator with no stake in the outcome is a more credible witness than either spouse. Our investigators spent their careers testifying in criminal court, where the standard of proof is higher than in a divorce. That background shows on the stand.
This is the standard every cheating spouse investigation we run is built to meet. Evidence is collected as if it will be challenged, because in a contested divorce it will be.
What gets thrown out (and can hurt your case)
Unlawfully obtained evidence is the fastest way to turn a strong case into a weak one. The judge may exclude it, and the spouse who gathered it can face criminal exposure or a civil claim. The common mistakes in New Hampshire and Massachusetts:
- Secret audio recordings. New Hampshire’s wiretapping law (RSA 570-A) requires the consent of all parties to record a private conversation. Massachusetts has the same all-party rule. A spouse who records the other on a hidden device, or plants a recorder in the car, has committed a crime, and the recording is useless in court.
- Logging into accounts. Reading a spouse’s email, texts, or social media by guessing a password or using a saved login is unauthorized access. Screenshots obtained that way are routinely challenged and can create a counterclaim.
- Trespassing for a photo. Filming through a window from inside someone else’s yard, or entering a residence you no longer live in, taints the evidence and the person who gathered it.
- Trackers on a vehicle you don’t own. Placing a GPS device on a car titled solely to your spouse or a third party raises serious legal problems in both states. We do not do it without written direction from counsel, and in most divorces it is unnecessary.
- “Evidence” from the client. Spouses often arrive with a folder of their own photos and screenshots. Some of it is usable, but it comes with a credibility problem: the person who took it has every reason to shade the story. Independent documentation does not have that problem.
How the evidence gets from the investigator to the judge
In a well-run case the investigator works for the attorney, or at least alongside them, from the start. That sequence protects the evidence and keeps the work focused on what the lawyer can actually use.
- Define the question. The attorney tells us what needs to be proven: an overnight pattern, a cash job, who is present during parenting time. We plan surveillance around that, not around curiosity.
- Collect and preserve. Original video files are preserved with their metadata. Copies go to counsel. Nothing is edited, enhanced, or trimmed.
- Report. A dated report and log go to the attorney, who decides whether to disclose it, use it in negotiation, attach it to a motion, or hold it for hearing.
- Testify if needed. Most divorce cases settle, and solid surveillance evidence is often the reason they settle early. When a case goes to hearing, the investigator authenticates the evidence and answers cross-examination.
The same process applies to a child custody investigation, where the question is usually about a parent’s conduct during their own parenting time rather than infidelity.
What to do before you hire anyone
- Talk to a New Hampshire family law attorney first if you can. Many will tell you exactly what they need documented.
- Stop gathering evidence yourself if any of it involves recording, passwords, or entering property. You may already have a problem to disclose to your lawyer.
- Hire a licensed investigator. New Hampshire licenses private investigators through the Department of Safety, and Massachusetts through the State Police. Ask for the license number. Ours are NH #M-2025-0424 and MA #LP1599A.
- Ask whether the investigator has testified in court and how they preserve video. The answers tell you whether the evidence will survive a hearing.
Frequently Asked Questions
Do I need to prove adultery to get divorced in New Hampshire?
No. Most New Hampshire divorces are granted on no-fault grounds. Proof of adultery matters when a spouse chooses to file on fault grounds, or when the conduct is relevant to property division, parenting, or credibility. Your attorney can tell you whether it is worth pursuing in your case.
Can a private investigator’s video be used in Family Division court?
Yes, when it was recorded lawfully from a place the investigator had a right to be and the investigator can testify to how and when it was made. Video from public streets, parking lots, and public businesses is accepted routinely. Video obtained by trespassing or secret audio recording is not.
Will the investigator have to testify?
Only if the case goes to a contested hearing and your attorney calls them. Many cases settle once the other side sees the evidence. When testimony is needed, the investigator authenticates the video and report and answers questions from both attorneys. Expect that possibility to be part of the engagement from the start.
Talk to a licensed investigator before you act
Donahue Investigative Services is licensed in New Hampshire and Massachusetts and led by former law enforcement with 56+ combined years of experience documenting evidence that holds up in court. Consultations are free and confidential. Call, or request a free consultation online.
Related reading: Is it legal to hire a PI to follow someone in MA or NH? · How much does a private investigator cost in NH and MA?
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