Due Diligence Defence

Many UK regulatory offences impose strict (or near-strict) liability on businesses and individuals for breaches of technical standards, and Parliament has repeatedly paired that strict liability with a due diligence defence rather than requiring proof of fault. Section 21 of the Food Safety Act 1990 supplies the paradigm example: 'it shall... be a defence for the person charged to prove that he took all reasonable precautions and exercised all due diligence to avoid the commission of the offence by himself or by a person under his control.' The burden of proof for the defence sits with the defendant (on the balance of probabilities), and s.21 contains additional deeming provisions (subsections (2) to (4)) letting certain distributors and retailers establish the defence by showing they reasonably relied on checks carried out by their supplier.

The same formula recurs outside food law: s.33(7)(a) of the Environmental Protection Act 1990, governing waste offences, provides an equivalent defence where the person charged proves 'that he took all reasonable precautions and exercised all due diligence to avoid the commission of the offence.' The near-identical wording across these regimes shows the due diligence defence functioning as a general legislative technique for regulatory strict-liability offences — food safety being simply the most litigated and best-known instance, not the only one.