When to Use a Private Investigator for Witness Tracing and Alibi Verification

A private investigator criminal defence in the UK enquiry can be useful in a specific set of situations: finding a witness who has gone quiet, verifying an alibi, or establishing where someone was. Here's when it's worth it, and when it isn't.

At Holborn Adams, we can assist in establishing whether witness tracing is a proportionate step and what the investigation needs to establish. This begins with an understanding of the evidence already available and identifying the particular point that a witness may be able to clarify. From there we can consider whether further investigation is appropriate including alibi verification or other forms of evidence gathering.

Witness Tracing: When and How It's Used

Tracing is usually needed when a potential witness has moved, changed contact details, or disappeared since the events in question. An investigator's role here is narrow and practical: establish current contact details through lawful means, and report back so the legal team can decide whether and how to approach them.

This is most useful when the witness's evidence is genuinely likely to matter, such as corroborating or undermining a specific account, rather than a general hope that "someone out there" might help. A solicitor should identify what that witness could actually establish before instructing tracing work, so the enquiry stays targeted rather than speculative.

Criminal defence solicitors can assess whether tracing a particular witness is likely to address an evidential gap. That assessment should come before investigative work begins, particularly where the available budget or timeframe is limited.

Alibi Verification in Practice

Alibi verification means testing whether an account of someone's whereabouts holds up against independently checkable facts: CCTV covering a location, transport records, receipts, phone cell-site data, or people who can confirm presence at a particular time. An investigator's job is to gather what's checkable and report the findings honestly, including when the evidence doesn't support the account given.

That last point matters. A negative or inconclusive result from alibi work isn't wasted. It stops a defence being built on an assumption that further investigation doesn't actually support, which is far better discovered before trial than during cross-examination.

Alibi work is also time-sensitive. CCTV in particular is often overwritten after a matter of weeks, so identifying and securing this kind of evidence early gives meaningfully better results than starting close to trial.

Criminal solicitors can help determine what needs to be established and whether an alibi requires independent verification before the evidence is relied upon.

Surveillance: What's Legally Permissible and What Isn't

Surveillance sits in the area investigators most need to get right. Private investigators in England and Wales aren't currently subject to a licensing scheme. The relevant provisions of the Private Security Industry Act 2001 were never brought into force for this activity, but that doesn't put surveillance outside the law.

Observing someone in a public place, where there's no reasonable expectation of privacy, is generally lawful. But surveillance that becomes persistent, or that causes the person alarm or distress, can amount to harassment under the Protection from Harassment Act 1997. This criminalises a "course of conduct" amounting to harassment, including monitoring someone's movements or communications. Any handling of personal data gathered during surveillance also has to comply with the Data Protection Act 2018 and UK GDPR.

In practical terms, an investigator can lawfully observe and record what happens in public. They cannot intercept phone calls or messages, access someone's device, or trespass to obtain evidence. Evidence obtained that way is not just legally risky. It can actively damage the case it was meant to help.

As a result, the role of a private investigator for criminal defence in the UK is not simply to gather as much information as possible. The work needs to remain proportionate, lawful, and directed towards a specific evidential issue.

Cost and Who Typically Pays

Costs vary with the scope and duration of the work. A short, defined tracing exercise costs considerably less than extended surveillance or a multi-day alibi verification enquiry. The client instructing the solicitor typically meets the costs directly, though this should be confirmed and scoped in writing before work begins, along with a clear fee estimate from the investigator.

Defined instructions matter here for cost as much as for legal risk. An investigator working to a specific, agreed-upon question is both more useful for evidential purposes and more predictable to budget for than an open-ended "see what you can find" instruction.

Working Alongside the Solicitor and Counsel

An investigator supports the legal strategy. They don't set it. The usual sequence is that the solicitor identifies the specific issue to be tested, defines the scope of the investigator's instructions, and then reviews the findings for relevance and reliability before they're used.

This matters particularly when the case is still pre-charge. Evidence traced or verified early can shape decisions about representations to the police or a bail application, as well as later trial preparation. See our page on bail applications and bail variation if bail is also a live issue in your case.

Criminal defence lawyers can assess how investigative findings fit within the wider defence strategy and whether they should be used in representations, witness evidence, or preparation for trial.

How Holborn Adams Supports Your Defence

• Identify whether witness tracing, alibi verification, or another form of investigation actually fits the evidential gap in your case.
• Define clear, focused instructions for any investigator we recommend.
• Review findings for relevance and reliability before relying on them.
• Keep investigative work within lawful surveillance and data protection limits.
• Integrate useful findings into witness evidence, bail representations, or trial preparation.

Our criminal defence solicitors assess the purpose of investigative work before it begins, helping ensure that resources are directed towards evidence that can genuinely assist the case.

Our criminal solicitors can review investigative findings alongside the wider evidence and advise on their relevance to your position.

Where specialist advocacy is required, our criminal defence lawyers can work with counsel to ensure relevant investigative material is properly incorporated into the wider strategy.

FAQs

When is it worth using a private investigator for witness tracing?

When a specific witness is likely to have evidence that materially matters to the case, but their current contact details aren't available, not as a general search for anyone who might help.

How does alibi verification actually work?

‍An investigator gathers independently checkable evidence, such as CCTV, transport records, or witness accounts, to test whether the account given holds up, and reports honestly even if it doesn't.

Can a private investigator legally follow someone?

‍Observation in a public place is generally lawful. It can cross into harassment under the Protection from Harassment Act 1997 if it becomes persistent or causes alarm or distress.

Can a private investigator access someone's phone or messages?

‍No. It is illegal to intercept communications or access a device without lawful authority and evidence obtained in this way is unlikely to be admissible.

Are private investigators licensed in the UK?

‍Not currently in England and Wales. Licensing provisions in the Private Security Industry Act 2001 cover investigators have never been brought into force, though data protection and harassment law still apply to their work.

Who pays for a private investigator in a criminal case?

‍Usually the client instructs the solicitor, once the scope of work and a fee estimate have been agreed in writing.

Is evidence from a private investigator admissible in court?

‍It can be, if it was lawfully obtained and is relevant and reliable. Evidence obtained through unlawful surveillance or unlawful data access is likely to be excluded.

How quickly should witness tracing or alibi checks start?

‍As early as possible. Evidence like CCTV is often overwritten within weeks, so delay can mean the evidence simply no longer exists to check.

Does a solicitor need to be involved in instructing an investigator?

‍Yes. The solicitor identifies the issue, scopes the instructions, and reviews the findings, so the work stays targeted and admissible rather than becoming a broad fishing exercise.

What if an investigator finds nothing to support an alibi?

‍That's still useful information. It prevents a defence relying on an assumption that further checking doesn't actually support, which is better established before trial than at cross-examination.

This article offers general information and does not constitute legal advice. For confidential advice about private investigators and evidence gathering, contact Holborn Adams to speak with a solicitor with experience in private investigator criminal defence in the UK.