In NHS 24 v Pillar, the EAT has ruled that an over-thorough investigation will not of itself render a dismissal unfair. It is for the decision-maker to decide what is relevant to their decision, and it is their state of mind that will determine whether dismissal was within the range of reasonable responses. The reasonableness of an investigation is relevant only where it results in the absence of relevant information being given to the decision-maker.

In this case the investigator had included in their report details of prior incidents of misconduct similar to the one being considered as grounds for dismissal; these had been dealt with by way of training rather than disciplinary sanction. The claimant did not challenge the tribunal’s ruling that it was fair for the decision-maker to take this information into account and, given this, it was perverse of the tribunal to find that the inclusion of the previous incidents in the investigation report was unreasonable.

The EAT agreed that, in contrast to an expired disciplinary warning, here there was no expectation that the prior incidents would not be referred to or that future incidents would not be regarded more seriously. (Prior case law has established that, given the expectation that an expired warning will not form part of the justification for dismissal, it can only be used to justify a decision not to impose a lesser penalty where the fresh misconduct being considered is sufficient on its own to justify dismissal.)