Why Legal and Procedural Foundations Matter

A workplace investigation is only as strong as the legal and procedural framework on which it is built. An investigator who gathers evidence diligently, interviews witnesses carefully and reaches well-reasoned conclusions can still produce an investigation that fails if the procedural foundations were wrong from the outset. Conversely, an investigation that is procedurally sound but analytically weak will also fail, because good process without good reasoning does not produce defensible outcomes.

The legal framework governing workplace investigations in England and Wales draws on several sources: the principles of natural justice, the ACAS Code of Practice on Disciplinary and Grievance Procedures, the duty to undertake a reasonable investigation established by employment tribunal case law, the rules on burden and standard of proof, and the role of HR in supporting fairness without compromising investigator independence. Understanding each of these is essential for anyone conducting, commissioning or overseeing a workplace investigation.

This chapter is part of the Workplace and Corporate Investigations Knowledge Guide. If you need an independent investigator see my independent workplace investigator page.

Natural Justice

Natural justice is the foundational legal principle governing fairness in workplace proceedings. It has two core requirements, both of which apply to investigations and to any hearing that follows.

The first is the right to know the case against you. A person who is the subject of an investigation must be told what they are being accused of with sufficient specificity to enable them to respond. Vague, shifting or conclusory allegations that do not identify the specific conduct in question fail this requirement. The subject must also be given access to the evidence relied on in sufficient time to prepare a response, and must have a genuine opportunity to respond before any decision is made.

The second is the right to an impartial decision-maker. The investigator must approach the matter without preconception and without a stake in the outcome. Any appearance of bias, even where no actual bias exists, is sufficient to undermine the credibility and fairness of the process. This requirement affects the choice of investigator, the way the investigation is managed, and the relationship between the investigator, HR and senior management throughout the process.

Natural justice is not a procedural technicality. It is a substantive requirement of fairness that tribunals take seriously. Investigations that fail to meet these requirements do not produce fair outcomes, however diligent the investigator may have been in gathering evidence.

The ACAS Code of Practice

The ACAS Code of Practice on Disciplinary and Grievance Procedures sets out the minimum standards of fair process that employers are expected to follow. The Code does not have the force of law, but employment tribunals are required to take it into account when assessing whether an employer acted reasonably. Failure to follow the Code without good reason can lead to an uplift of up to 25 percent in any compensation awarded where a claim succeeds.

The Code’s requirements include that employees are informed in writing of the allegations against them, that they are given sufficient time to prepare their response, that they have the right to be accompanied at disciplinary and grievance hearings by a trade union representative or a work colleague, that hearings are conducted by someone not previously involved in the matter, that decisions are communicated in writing with clear reasons, and that employees are given the right to appeal.

Beyond these minimum requirements, the Code reflects a broader principle: that fair process is not a bureaucratic obstacle to reaching the right answer but the means by which the right answer is reached. Investigations that treat procedural requirements as inconvenient formalities to be managed rather than genuine safeguards to be respected tend to produce weaker findings and less defensible outcomes.

The Duty to Undertake a Reasonable Investigation

Employment tribunals have consistently held that employers must conduct a reasonable investigation before making disciplinary decisions. The leading case is British Home Stores Ltd v Burchell [1978] IRLR 379, which established that where an employer dismisses an employee for misconduct, the employer must show that it had a genuine belief in the employee’s guilt based on reasonable grounds, having carried out as much investigation as was reasonable in the circumstances.

This is known as the Burchell test. It has three elements. First, the employer must genuinely believe the employee is guilty. Second, that belief must be based on reasonable grounds. Third, the employer must have carried out a reasonable investigation before forming that belief. All three elements must be satisfied. A genuine belief formed without a reasonable investigation, or reasonable grounds formed through an unreasonable process, will not meet the test.

Importantly, the standard is reasonableness, not perfection. Tribunals do not expect flawless investigations. They do expect investigations that are proportionate to the seriousness of the allegations, that examine the relevant evidence, that give the subject a fair opportunity to respond, and that reach conclusions based on reasoning rather than assumption. Where an investigation falls significantly below that standard, the decision that follows it is likely to be found unfair regardless of wheth