People often price both at the same time, which suggests they are alternatives. They are not really. A private investigator gathers external evidence about what someone does; a credibility test examines whether the account someone gives is truthful.
Which you need depends on whether you have a suspicion or a denial.
Surveillance produces observations: where someone went, who they met, timings, sometimes photographs. It works on behaviour that happens in observable places and it says nothing about the past.
A lie detector test produces a scored outcome on specific factual statements — including about the past, which surveillance cannot reach. It requires the person's consent, which surveillance does not.
Investigators typically charge by the hour or the day, often with two operatives and vehicle costs, and a meaningful surveillance package runs over several days with no guarantee of capturing anything. Costs escalate with time.
A test is a fixed cost and a fixed timescale: £495 for a single test, all-inclusive within 50 miles of our Darlington base and 60p per mile beyond, with a verbal result the same day. For many people that predictability is the deciding factor.
If your partner or employee denies something specific and you need to know whether the denial holds, test. If nobody has denied anything yet, or you need to establish what is happening now rather than resolve a disputed account, surveillance is the better tool.
For historic questions — what happened last year, whether an old relationship really ended — surveillance has nothing to offer and testing is the only practical route.
It happens more often than you would expect, usually in sequence. Surveillance establishes something concrete, the person gives an explanation, and a test settles whether the explanation is truthful. In workplace cases the order is often reversed: internal evidence first, then voluntary testing to narrow a pool.
Whatever you choose, be clear on what a positive answer changes for you before you spend anything.
The distinction is simpler than it looks. Surveillance answers "what is happening now" and produces photographs, timings and movement logs. Testing answers "what has already happened, according to this person" and produces a scored result against agreed questions. Neither substitutes for the other.
Cost behaves very differently too. Investigation is charged by time and can run for weeks with no guarantee of a usable result, because it depends on the subject doing something observable while being watched. Our testing is a fixed £495 base fee with travel included in the quote, in one visit, with the result explained the same day.
Where people combine them, the productive order is usually investigation first and testing second. Surveillance gives you dates, places and names, and those turn vague worries into precisely the sort of closed factual question a test handles well.
It works the other way round as well. A test that clears specific concerns often ends the matter without the cost or intrusion of surveillance at all, which is why we frequently suggest it as the cheaper first step when the question is about the past rather than the present.
Usually, and it is far more predictable — a fixed fee and a same-day result rather than open-ended daily rates.
No. Testing requires written informed consent on the day. If you need information without the person's knowledge, that is investigation work, not testing.
Yes. We regularly test where an investigator or a solicitor has established the factual dispute that needs resolving.
Documented evidence from an investigator generally carries more weight in UK proceedings. Test results are not primary evidence of fact, though solicitors do use them to inform negotiations and to decide where to press.
Usually, and more predictably. A test is a fixed fee for one visit, whereas surveillance is charged by the hour or day and may need repeating before anything useful is captured.
Services · Pricing · How it works · Book a test · Contact