Private Investigator common mistakes
Private Investigator · Understand the traps and how to avoid them.
Accepting an out-of-state assignment and immediately conducting witness interviews or physical surveillance there, relying on the PI licence issued by the home state and never checking whether the assignment state requires its own licence, registration, or reciprocity filing.
Exam prep is dominated by federal law, evidence rules, and general ethics, so candidates memorise their home state's licensing statute and assume licensure is portable; instructors and study guides rarely drill the multi-state matrix.
What to do instead
Build and memorise a per-state matrix before the exam: does the state license PIs at all, is there a reciprocity or registration requirement, what activities count as 'investigation' (record retrieval vs. surveillance vs. interviews), and what the penalty is for unlicensed practice. On the job, treat every cross-border assignment as a licensing question to be answered in writing before any work begins.
Allowing an unlicensed employee or trainee to conduct live witness interviews or surveillance while calling the arrangement 'supervised,' treating the licensed investigator's oversight as a legal substitute for the employee's own credential.
The apprenticeship model is how most firms actually train people, so it feels normal and low risk; candidates also confuse 'working under a licence' with 'being covered by a licence.'
What to do instead
Learn the specific task-level exemptions and prohibitions in the licensing statute: which functions may be performed by unlicensed clerical or support staff, which require an individual licence, and whether the state recognises a registered employee or intern category. Supervision does not cure unlicensed activity unless the statute expressly says it does.
Running a pretext call or submitting a records request that impersonates the data subject or a person with authority, such as phoning a utility posing as the account holder to confirm an address or service dates, without any written analysis of the lawful basis for that specific source.
Pretexting works quickly and is standard in the field's folklore; candidates memorise 'no pretexting' as a slogan but never map the rule onto specific record types and specific statutes, so each new source looks like a grey area.
What to do instead
Use a lawful-basis memo per data source: identify the exact statute or exception (permitted purpose, consent, public record, subpoena) before the request goes out. Memorise that obtaining financial records by false pretenses is a federal crime, that driver and motor-vehicle records have their own permitted-purpose list, and that 'publicly available' is not the same as 'unrestricted.' If the memo cannot be written in three sentences, do not make the call.
Receiving a document, phone, or hard drive from a client or witness and putting it in a case folder without a signed receipt, then describing it in the report as 'evidence received' with no record of who held it, when, or in what condition.
Investigators are trained to find and evaluate information, not to think of themselves as evidence custodians; the item feels like a work product rather than an exhibit, and paperwork at intake feels like a delay.
What to do instead
Create a one-page intake form used on every handoff: date and time, description and condition, source identity and signature, photographer, seal or bag number, and storage location. Log every subsequent transfer the same way. For digital items, photograph the device, record serial numbers, and compute a hash at intake before any examination.
Running mobile surveillance for hours with no contemporaneous written log, then testifying or reporting that 'the video shows' the subject doing something on a given date, with no record of when the camera was on, where the vehicle was, or who held the media card in between.
Video and photographs look self-authenticating, so candidates assume the recording and the file metadata will speak for themselves; the log feels redundant while the investigator is driving.
What to do instead
Run a parallel written surveillance log during the operation: clock-synchronised start and stop times, location checkpoints, odometer or landmark confirmations, breaks, and any counter-surveillance indicators. Document the media card's custody from removal to download, and keep the original files unedited alongside any working copies.
Writing up a witness interview as a first-person statement in the witness's voice, drafted by the investigator from notes, then asking the witness to sign it, without recording the exact questions asked or flagging which sentences are the investigator's paraphrase.
It produces a cleaner, more useful document than verbatim notes, and a cooperative witness usually signs without protest, so the shortcut appears harmless.
What to do instead
Preserve the question-and-answer structure or have the witness write in their own hand. Where a summary is unavoidable, label it a summary, attribute each assertion to a specific answer, have the witness initial each page and each correction, and make clear whether the document is given under penalty of perjury. Note the interview setting, who was present, and any invocation or request to stop.
Describing an interview with a suspect as requiring or not requiring Miranda warnings without first establishing who the questioner is and whether any state actor is involved, or conversely assuming that because the investigator is private, no rules of any kind constrain the questioning.
Television and popular summaries present Miranda as a universal rule of interviewing; candidates rarely see the 'state action' and 'custodial interrogation' elements tested explicitly.
What to do instead
Memorise the two-part trigger: custody plus interrogation, applied to state action. Then learn the private-actor exceptions that can convert conduct into state action, such as working at the direction of police, an off-duty officer in an official role, or an agency relationship. Document your status and the client's instructions in the file so the answer is provable later.
Writing the report with conclusions and character judgments in the narrative, for example 'the subject appeared nervous and was obviously lying,' and stating a source's hearsay as established fact.
The investigator has already done the synthesis in their head, so the conclusion feels like the most valuable content; separating observation from inference reads as weaker writing.
What to do instead
Apply a strict three-column discipline: what was directly observed, what a source said (attributed and quoted), and what the investigator infers (labelled as inference or omitted). Replace adjectives with conduct: not 'nervous' but 'tapped his foot and looked at the door four times in two minutes.' Keep original field notes and make corrections with a single line, initials, and date.
Stepping past a closed gate or 'no trespassing' sign to reach a back door for a knock-and-talk, or using a ladder or drone to photograph over a fence into a residential yard.
The open-view and plain-sight ideas get overgeneralised into 'anything visible from outside is fair game,' and the curb-appeal shortcut is much faster than obtaining consent or a lawful vantage point.
What to do instead
Learn the curtilage factors and apply them before every approach: proximity to the dwelling, enclosure, use of the area, and steps taken to shield it from view. Limit implied consent to the normal path to the front door, leave immediately when asked, and check the state's drone statute for altitude, privacy, and harassment provisions before any aerial observation.
Starting work on a verbal understanding with no signed engagement letter, and depositing the client's advance retainer into the firm's general operating account alongside business revenue.
Small investigative firms run on speed and trust, and the retainer feels like earned cash rather than someone else's money held in trust; the paperwork feels like something to do after the case closes.
What to do instead
Adopt a written engagement checklist used on every matter: scope and deliverables, fee structure and expenses, no guarantee of a particular outcome, confidentiality, file-retention and termination terms, and the client's signature. Hold all advance funds in a separately reconciled trust or client-funds account until earned, and calendar the statutory or contractual retention period for each closed file.