What surveillance is, in practice
It is planned observation of a person in public and publicly accessible places, over defined windows, with contemporaneous dated notes and, where professional and practicable, photographic or video material.
What it is not is continuous monitoring. Nobody is watched twenty-four hours a day; that would cost more than almost any client would pay and would produce mostly irrelevant material. Effective surveillance concentrates on the windows in which the question can actually be answered.
Why window analysis decides whether it works
Before any fieldwork, the useful exercise is identifying when and where the behaviour in question would have to occur. If a client's concern is unexplained absences on Tuesday and Thursday evenings, observation on a Sunday afternoon cannot answer it, however many hours are logged.
This is the main reason open-ended surveillance disappoints. Clients pay for days, and days spent in periods that cannot produce anything are days wasted. Any investigator quoting surveillance without first establishing the windows is selling hours rather than an answer.
What is professional, and what is not
Professional: observing a person in public; documenting movements, timings and meetings; photography from a public vantage point; vehicle observation; establishing whether an address is occupied; static observation of premises from a professional position.
Not professional: recording inside a private dwelling without consent; entering private property to obtain a vantage point; placing a GPS tracker on a vehicle you have no authority over; phone tracking or interception; and anything that crosses from establishing a fact into harassment.
The distinction matters beyond legality. Material obtained unproperly is routinely excluded in court and can shift proceedings against the party who produced it.
How many days you actually need
For a single event to be documented, often two to four days placed in the right window. For a pattern to be established — which usually carries more weight, because a single occasion is more easily explained — eight to fifteen days spread across several weeks is more realistic than the same number consecutively.
Spreading matters. Three consecutive days tell you about three days. The same three days spread across three weeks tell you whether something is routine.
What surveillance produces, and what it does not
It produces: a dated chronology of movements and meetings; photographic or video material with recorded provenance; confirmation of whether an address or workplace is genuinely used; and a documented pattern if one exists.
It does not produce: what was said in a private conversation; what happened inside a building; the nature of a relationship beyond what public conduct shows; or certainty about intent. An observation that two people met four times establishes that they met four times. Anything beyond that is inference, and a report that presents it otherwise is not doing you a favour.
Talk it through before you commit to anything
If this guide leaves you unsure whether your situation needs an investigator, the quickest way to find out is a short call. It is free, and you will get a direct answer — including when the answer is that nothing should be commissioned.