detectiveIn March, the Supreme Court handed down its decision in Hayes v Willoughby, The Court was called upon to clarify the scope of the defence against harassment outlined in the Protection from Harassment Act 1997, s 1(3)(a). The section provides a defence for conduct that might otherwise be harassment if it was pursued with ‘the sole purpose of preventing or detecting crime.’ There is also a defence under s 1(3)(c) that in the particular circumstances the pursuit of the course of conduct was reasonable.


Mr Willoughby alleged that his former employer Mr Hayes had been guilty of a number of offences of fraud and embezzlement. He entered into lengthy correspondence with a number of law enforcement agencies despite authorities concluding upon investigation that there was no evidence to support Mr Willoughby’s allegations.

At first instance His Honour Judge Moloney QC concluded that the course of conduct exceeded “even the widest limits of reasonableness and became unreasonable and excessive”. He ruled however that Mr Willoughby had established a statutory defence under s 1(3)(a). Mr Willoughby had a genuine belief that the claimant had been guilty of fraud and that was sufficient to amount to a defence. Parliament did not intend that it was necessary for a defendant to justify his conduct, for the purposes of section 1(3)(a), as reasonable.

The Court of Appeal overturned the decision and ruled that s 1(3)(a) is confined to a course of conduct the purpose of which is preventing or detecting crime. There is no reason to protect a defendant whose course of conduct constitutes harassment because one of the purposes is the prevention or detection of crime unless his course of conduct was reasonable. A finding that the campaign was misconceived or became unreasonable does affect the defence: such a finding would make it highly unlikely, if not impossible, for anyone pursuing such a campaign to show that the purpose of the course of conduct came within the sub-section.

The Supreme Court decision

The Supreme Court dismissed the appeal, but did not endorse the judgment of the Court of Appeal. Lord Sumption gave the leading judgment, and ruled that there was no distinction between the purpose of the conduct and the purpose of the alleged harasser. The issue was by what standard the purpose was to be assessed. A test of reasonableness was deliberately not included in s 1(3)(a) as it was in other sections of the Act. A wholly subjective test, however, was not appropriate either. The necessary control mechanism was held to be the concept of rationality:

“Rationality is not the same as reasonableness. Reasonableness is an external, objective standard applied to the outcome of a person’s thoughts or intentions. The question is whether a notional hypothetically reasonable person in his position would have engaged in the relevant conduct for the purpose of preventing or detecting crime. A test of rationality, by comparison, applies a minimum objective standard to the relevant person’s mental processes. It imports a requirement of good faith, a requirement that there should be some logical connection between the evidence and the ostensible reasons for the decision, and (which will usually amount to the same thing) an absence of arbitrariness, of capriciousness or of reasoning so outrageous in its defiance of logic as to be perverse.” [para 14]

Lord Sumption stated that rationality is a ‘familiar concept in public law’, but not the same as either reasonableness or Wednesbury unreasonableness. The test of rationality, when applied to the facts, suggested that the appellant’s conduct was no longer guided by any assessment of evidence, nor was there a rational connection between his supposed purpose and acts.


It was suggested in the case preview that that the reasoning of the Court of Appeal was fairly persuasive, in particular the observation that “the defence is not designed to enable any Tom, Dick or Harry to set himself up as a vigilante and harass his neighbours under the guise of preventing or detecting crime”. Lord Mance echoed this sentiment:

If one asks whether Parliament can really have intended there to be no limits to the pursuit of a course of conduct for the purpose of preventing or detecting crime, no matter how irrational, perverse or abusive its pursuit may have become, the answer I would give is negative. Mere unreasonableness is not the limit. But the law recognises looser control mechanisms such as complete irrationality, perversity, abusiveness or, indeed, in some contexts gross negligence.” [para 22]

In addition, it would seem counterintuitive for the defence to apply in the example given in the judgment at first instance, that is to a schizophrenic under the delusion that someone is about to commit murder. The outcome of the decision was perhaps unexpected. Lord Reed’s dissent is well worth a read however, as it does highlight some concerns with the majority judgment, which appears to have been guided by a largely purposive reading of the Act. The purposive reading meant that the Court was not perhaps as cautious with its interpretation of legislative semantics as might be expected.

There are two potential concerns with the majority judgment. Firstly, where does the concept of ‘rationality’ come from?  Lord Sumption states that the concept is a ‘familiar’ in public law and also increasingly common in ‘contractual disputes’. However, as Lord Reed suggests, what constitutes ‘rationality’ is a little unclear, and this is important as section 1(3)(a) and similarly worded provisions elsewhere in the Act provide defences to criminal as well as civil liability:

“I cannot readily bring to mind any example, in any context, of a statutory requirement not of reasonableness but of rationality, the latter being understood as conceptually distinct from the former  . . . I would be slow to infer that criminal liability was intended to turn upon the subtle distinction between what is unreasonable and what is irrational . . . Are juries to be required to determine where that boundary lies? It may be that appropriate directions can be devised by judges, although I do not underestimate the difficulty of devising directions which accurately reflect Lord Sumption’s analysis. I have to confess that I am not sure that I understand the distinction drawn at para 14 between on the one hand “rationality [as] a familiar concept in public law”, which “is not the same as reasonableness”, and on the other hand “the broader categories of Wednesbury unreasonableness”; or the statement that there should be “an absence of arbitrariness, of capriciousness or of reasoning so outrageous in its defiance of logic as to be perverse”.” [para s26 & 28]

If the rationality test is as common as Lord Sumption suggests one might expect its definition to be a little clearer in this context.

Secondly, if Parliament had intended to include a form of rationality requirement in s 1 (3) (a) then why was it not stated in the Act? By reading in “the necessary control mechanism” of rationality the Court indirectly modifies the content of the Act to a significant extent, and in effect extends criminal liability under the Act by narrowing the scope of the defence. Lord Reed argues that the majority judgment will threaten the activities of investigative journalists and public agencies exercising investigative powers, “whose conduct may be equally upsetting to those whom they are investigating and will also, as a result of this decision, be susceptible to challenge in the courts.” It is suggested that the activities of investigative journalists and public agencies would be unlikely to fail the rationality test proposed by Lord Sumption. Lord Reed is correct however to highlight the implications of a general rationality requirement. Arguably, the Court focused on the narrow issue of the defence in its current form applying to persons laboring under delusions without considering the wider potential consequences of reading in a general rationality requirement.

It will be interesting to see how those employing the defence in future will be able to show that their behavior was ‘rational’ and whether the defence will have the problems in jury trials that Lord Reed suggests. It is unlikely that we have seen the last of appeals concerning s 1 (3) (a) of the Act.