Private investigators work by gathering evidence through surveillance, interviews, database research, and open-source intelligence (OSINT). Most PI work falls into two categories: cases tied to the legal system (where evidence must meet courtroom standards) and private cases initiated by individual clients. The specific methods depend on the case type, applicable state laws, and what the client actually needs to prove.
The job looks different from the outside than it does from the inside. What PIs actually spend their time doing — the evidence standards they have to meet, the legal lines they can’t cross, the prep work before a stakeout even begins — is more procedural and more interesting than anything Hollywood bothers to show. This page breaks down how private investigators work across the most common case types, from the first client call to the final report.
Two Kinds of PI Work: Legal System vs. Private Cases
Most PI assignments fall into one of two categories, and the distinction matters from the moment you accept the case.
Cases involving the legal system require evidence that will hold up in court. Law offices, insurance companies, government agencies, and fraud departments hire PIs specifically to build evidentiary records. The standard you’re working toward isn’t “I’m pretty sure” — it’s “this will survive cross-examination.” Understanding the specific law that applies to your case tells you exactly what evidence you need to gather, and just as importantly, what you don’t need. In an infidelity case headed for divorce court, for example, you don’t need hidden cameras or recorded audio if the legal standard for reasonable suspicion only requires placing the parties at the same location with sufficient time and opportunity. Knowing that saves you hours of work and keeps you on the right side of surveillance law.
Private citizens typically initiate cases outside the legal system and may never see a courtroom. Missing persons, suspected infidelity (for personal confirmation rather than litigation), and locating someone who owes money all fall here. These cases require clear communication with your client upfront: what do they actually want to know, what can you realistically deliver, and what will you do if the evidence points somewhere uncomfortable? Even if a case starts as purely personal, it can end up in court, so staying within legal boundaries from day one is never a bad idea.
Common Client Types for Legal Cases
- Law offices and attorneys
- Insurance carriers investigating claims
- Employers with fraud or loss-prevention concerns
- Government oversight and audit departments
- Accounting firms handling asset investigations
How Private Investigators Work: Core Methods
Regardless of case type, PI work draws from a relatively consistent set of methods. The combination you use depends on what the case requires and what your state’s law permits.
Surveillance and Stakeouts
Surveillance is the bread and butter of PI work. You’ll use it in fraud cases, custody disputes, infidelity investigations, insurance claims, and more. The goal is always the same: gather documented, time-stamped evidence of what a subject is actually doing. Surveillance laws vary by state. What’s permissible in one jurisdiction may not be in another, so licensed PIs are expected to know the rules that apply where they operate.
Most surveillance is conducted from a parked vehicle. Location matters: close enough to maintain a sightline, far enough that a neighbor or patrol officer checking on a parked car doesn’t blow your position. About five houses back is a common working distance, though every location is different. The basics you bring: binoculars, a camera or video camera, a voice recorder, a notepad and pen as backup, and enough food to last the shift without leaving your post. You don’t break for drive-through. You plan for bathroom logistics before you start. You keep the engine off so the exhaust doesn’t give you away. Smoking will do the same. Don’t do it on a stakeout.
Every observation gets logged with a timestamp. When your subject makes contact with another person, you note identifying details for each. Your mission ends when you have the evidence you need, or when you’ve conducted a thorough enough investigation to document its absence. Both outcomes are reportable. The client decides whether to continue.
Interviewing and Questioning
Good interviewing technique is one of the skills that separates effective PIs from mediocre ones, and it’s something you develop over time. Always bring a notepad and a recording device. Consent requirements for recording vary significantly by state. Federal law requires at least one-party consent, but roughly a dozen states require all parties to consent before a conversation is recorded. Know your state’s rules before you hit record, and get documented consent regardless. Verbal acknowledgment on the recording itself is standard practice. Video is better than audio alone because body language conveys information a transcript can’t.
The approach with a new interview subject isn’t to start with the hard questions. You start on neutral ground: where they grew up, where they went to school, topics you already know the answers to. What you’re doing is establishing a baseline: what does this person look like when they’re telling the truth? Once you know that, you’re in a better position to notice when something shifts. When you eventually move toward the sensitive material, you have a frame of reference. If the subject gets tense and shuts down, you can back off to safe territory and reset before trying again.
Digital Investigation and Open-Source Intelligence
A significant portion of modern PI work happens on a screen before a PI ever leaves the office. Open-source intelligence (OSINT) refers to information gathered from publicly available sources, such as social media profiles, court records, property records, business filings, news archives, and commercial databases. A skilled PI can build a substantial picture of a subject’s associations, whereabouts, financial situation, and history before the first stakeout begins.
Skip tracing (locating a subject who doesn’t want to be found) relies heavily on database work. Commercial skip-tracing platforms aggregate public records and credit header data to surface current addresses, phone numbers, and associated individuals. Social media adds behavioral context: where people post, who they’re with, and the patterns their activity suggests. This isn’t surveillance in the legal sense, but it informs surveillance. You go into a stakeout knowing where to look and what to expect.
Digital investigation also applies to computer forensics work, which is its own specialty within the field. Corporate clients, attorneys in divorce cases, and employers investigating data theft are the typical clients. For a broader look at how PIs specialize, see our overview of private investigator careers and role types.
Background Checks
Background check assignments are among the most common and consistent work PIs take on. Employers hire investigators for in-depth pre-employment screening that goes beyond what automated online services provide. Attorneys use them to vet witnesses and opposing parties. Individuals run them on potential business partners or people they’ve met online. The work involves obtaining criminal history, civil court records, driving history, employment verification, education verification, and, sometimes, credit or financial history, depending on the purpose and applicable law. The Fair Credit Reporting Act (FCRA) governs when and how certain consumer data can be used, so PIs doing background checks for employment or tenant screening purposes need to understand their compliance obligations.
The Most Common Cases, Start to Finish
Child Custody Investigations
Child custody cases are among the most intensive work a PI takes on. You’ll almost always be working alongside an attorney, who handles depositions and legal filings while you handle field investigation. The attorney can tell you exactly what standard the court applies, including what evidence actually moves a judge, so you’re not gathering information that won’t matter.
The parties involved are emotionally raw, which means everyone you interview will tell you whatever makes their side look better. Your job isn’t to pick a side. It’s to document facts. The final report you produce may be submitted to a court and potentially entered into the record of a child’s custody arrangement. That’s worth keeping in mind in every case.
What you’re looking for falls into a few categories:
- Competence and condition of the subject: Evidence of substance abuse, criminal behavior, unstable relationships, or unemployment
- Environmental safety: Unsafe living conditions, presence of dangerous individuals, evidence of abuse or neglect
- Compliance with existing orders: Whether current custody agreements and court orders are actually being followed
- Child well-being: Interviews with teachers, coaches, and community members; academic performance; stated preferences of the child
These cases can run weeks to months and involve the full range of PI work: surveillance, interviews, database research, and written reporting. You may be called to testify.
Process Serving
Process serving is the delivery of official legal documents to a named individual. It starts as a locate job and ends with a face-to-face handoff. Your client is typically an attorney. Your subject may be actively avoiding service, so your first task is to find them.
Once you’ve located the subject, the next requirement is identity confirmation. You need to verify you have the right person before you hand over legal documents. PIs develop their own techniques for this, getting a subject to confirm their name and a personal identifier (date of birth, graduation year, or similar) without revealing their purpose. The method is essentially a pretext: you approach as a delivery person, a contest representative, or some other plausible reason to be at the door. The subject confirms who they are. You serve the papers, document that service, and get clear. One important distinction: using a pretext to confirm identity for service purposes is generally permissible. Using deception to obtain protected financial, medical, or account information is a separate matter, one that federal law (the Gramm-Leach-Bliley Act, among others) prohibits. Back at the office, you write up a confirmation report for the attorney who hired you: the subject identified, the papers served, and the time and date of service.
Internal and Employee Investigations
When a business is consistently coming up short on inventory, cash, or time (or suspects an employee of misconduct), it brings in a PI. Your first meeting is with the owner or manager: what specifically are they seeing, what do they suspect, and what outcome are they looking for? Set realistic expectations for what you can deliver and the timeframe.
The work typically involves interviewing employees in the target department, reviewing personnel records, examining security footage, and, at times, installing additional surveillance equipment. If the client wants the option to pursue criminal or civil charges, you work from day one with that evidentiary standard in mind. A good interviewing sequence with the right employees can often identify the core problem quickly. Once you can make a case against one person, that person frequently becomes a path to understanding the broader picture. Internal investigations typically run 80 to 120 hours from kickoff to final report.
Insurance and Benefits Fraud
Insurance companies, employers, and government agencies hire PIs to verify that people collecting disability, workers’ compensation, sick leave, or other benefits actually qualify for them. The work is almost entirely surveillance-based: you’re documenting physical activity that contradicts a claimed injury or condition. A subject who claims to be bedridden with a back injury but is observed loading equipment into a truck, or someone claiming blindness who is photographed driving, generates exactly the kind of time-stamped visual evidence these cases require.
Tailing a Target
Following a subject in a vehicle is statistically one of the more hazardous things a PI does, not because of anything dramatic, but because you’re driving. At the same time, your attention is split between the road and a moving target. That demands preparation. Equipment should be hands-free: a dash-mounted camera, a voice-activated recorder, and Bluetooth for your phone. You’re not picking up a camera when something happens. Everything is being recorded automatically.
The balance to maintain is distance versus visibility. Too far back and you lose them at a light. Too close and they make you. Practical tips: wear clothing that blends with your car’s interior color, use a vehicle with tinted windows, stay out of the direct line of sight of the rearview mirror, and scout the route in advance if the lead allows it. In cities with transit systems, mobile surveillance on foot or via public transit requires its own preparation: tickets or passes in hand, nothing that forces you into a queue when your subject is on the move.
What Private Investigators Cannot Legally Do
The legal limits of PI work are as important to understand as the methods themselves. Operating outside them risks your license. It can expose you and your client to civil liability and criminal charges, and it can destroy the evidentiary value of everything you’ve gathered.
A few of the most commonly misunderstood limits:
- Wiretapping and recording without consent: Federal law (the Electronic Communications Privacy Act) prohibits recording phone calls or electronic communications without at least one party’s consent. Many states go further, requiring all parties to consent. “One-party” vs. “all-party” consent varies by state and matters enormously. PIs cannot tap phones, intercept texts, or access email accounts without authorization.
- Accessing private records without authorization: Social Security records, medical records, financial account data, and sealed court records are not accessible to PIs through legal means absent a court order or the subject’s consent. Anyone offering to pull this data through unofficial channels is either breaking the law or selling you garbage.
- Trespassing: PIs have no special authority to enter private property. Surveillance in public spaces is legal. Setting foot on private property without permission is not.
- Impersonating law enforcement or government officials: This is a crime. PIs cannot represent themselves as police, federal agents, or government investigators to obtain information or compliance.
- Hacking and unauthorized computer access: The Computer Fraud and Abuse Act applies to PIs the same way it applies to anyone else. Accessing accounts, systems, or devices without authorization is illegal, regardless of what information they may contain.
For a fuller breakdown of what state and federal law actually permit, see our guide to private investigator laws. If you’re working toward your own license, the PI licensing requirements by state cover what each state board requires.
What to Expect When You Hire a Private Investigator
If you’re on the other side of this, considering hiring a PI rather than becoming one, here’s the short version of how engagements typically work.
A reputable PI will start with a consultation: what are you trying to find out, what do you already know, and what do you intend to do with the information? They’ll give you a realistic assessment of what’s achievable and what it will cost. Most investigators charge by the hour plus expenses, with retainers common for ongoing work. Rates vary widely by market and specialty.
You’ll sign a contract that outlines the scope of work, rate structure, and what deliverables you’ll receive. At the conclusion of an investigation, you receive a written report, often accompanied by supporting documentation, such as photographs, video, or records. If the case is headed to court, your PI may be called to testify about their methods and findings.
What a PI cannot do for you is the same as what they can’t do period: no illegal surveillance, no unauthorized record access, no impersonation. A PI who offers to provide those things is a liability, not an asset.
Frequently Asked Questions
How do private investigators find information on someone?
PIs use a combination of surveillance, interviews, public records searches, commercial databases, and open-source intelligence (OSINT) from social media and other publicly available sources. The specific methods depend on what the case requires and what applicable law permits. For locating individuals, skip-tracing databases are a primary tool.
What can a private investigator legally do?
PIs can conduct surveillance in public spaces, interview witnesses and third parties, search public records, run background checks, serve legal documents, and gather evidence for court or private use. What they can’t do is wiretap communications without authorization, access private records illegally, trespass on private property, or impersonate law enforcement.
How long does a private investigation take?
It depends entirely on the case type. A process-serving assignment might wrap up in a day once the subject is located. A surveillance-based insurance fraud case could run from a few days to several weeks. Child custody investigations often take one to three months. Internal employee investigations typically run 80 to 120 hours of work. Your PI should give you a realistic estimate at the outset based on the specifics of your situation.
Do private investigators work with law enforcement?
PIs operate independently and have no law enforcement authority. They can’t make arrests, compel testimony, or access law enforcement databases. That said, the information they gather is regularly used in court proceedings alongside law enforcement evidence. Attorneys often hire PIs to supplement public investigations or pursue leads that police don’t have the resources to follow.
Can a private investigator follow someone?
Yes. Surveillance in public spaces, including following a subject in a vehicle or on foot, is legal. PIs cannot follow someone onto private property or use methods that cross into stalking under state law. Most states have specific statutes governing surveillance that licensed PIs are required to know and comply with. See our surveillance fundamentals guide for more details.
How much does it cost to hire a private investigator?
Rates vary by location, specialty, and the scope of work involved. Most PIs charge hourly plus expenses, with retainers for ongoing investigations. Straightforward background checks or process-serving jobs tend to be lower-cost; ongoing surveillance or complex fraud investigations tend to be higher-cost. Getting a detailed written scope and rate structure before signing is standard practice.
Key Takeaways
- Two tracks of PI work: Cases tied to the legal system require court-quality evidence; private cases focus on delivering the information a client needs.
- Core methods are consistent: Surveillance, interviews, database research, and OSINT apply across virtually every case type.
- Legal limits are non-negotiable: PIs cannot wiretap communications, access private records without authorization, trespass, or impersonate law enforcement.
- Digital investigation is modern PI work: Skip tracing, OSINT, and public records searches often do as much heavy lifting as field surveillance.
- The final product is always a report: Every investigation ends with documented findings. In court cases, you may also be called to testify.
- Understanding the applicable law shapes the investigation: Knowing exactly what evidence standard you’re working toward tells you what to gather and what you don’t need.
Ready to start your path to becoming a licensed PI? Find private investigator schools, programs, and education options in your state.