[Thanks to Ed McFarlane of Deminos HR for preparing this case summary]
No, says the EAT in Wincanton Group v Stone, unless satisfied that an earlier warning was issued in bad faith or was manifestly inappropriate.
The Claimant (a lorry driver) was dismissed for misconduct after a serious driving accident, on the back of a written warning for different misconduct. The employment tribunal found the dismissal unfair, having considered that the Claimant challenged the earlier warning (here by a tribunal claim) and how it arose, although that warning was found to be valid.
The EAT overturned the finding of unfair dismissal, remitting the case for re-hearing and set out guidance for tribunals dealing with dismissals involving accumulated warnings (paragraph 37).
The overall question is the reasonableness of the employer's act of treating conduct as a reason for dismissal under Section 98(4) ERA, and tribunals should:
But tribunals are not "going behind" a warning by taking into account the factual circumstances that gave rise to it, e.g. considering whether the types of conduct giving rise to an earlier warning and ultimate dismissal were similar or not, and tribunals may consider the particular features of a situation, as well as the consistency of the employer's approach.