Ben Williams sets out the general principles when it comes to decisions to prosecute.
The essential principle is that it is for prosecutors to decide when to prosecute. The courts will be slow to intervene. Provided that the decision is taken rationally and not capriciously, it will be secure against challenge.
The primary means by which a decision may be challenged is an application to stay the resulting proceedings as an abuse of process. Judicial Review should be sought only in exceptional circumstances, such as where there has been dishonesty or bad faith – R. v Director of Public Prosecutions Ex p. Kebilene  1 Cr. App. R. 275;  2 A.C. 326 (HL).
When application is made for a stay, it is only where abuse is plainly shown that a court should intervene.
Regard must be had by a regulator to its enforcement policies, which typically refer to or adopt the DPP’s Code for Crown Prosecutors and the essential two limb test of evidential sufficiency and the public interest.
However, in R v A  EWCA Crim 434. Lord Judge CJ made it clear that, provided the exercise of prosecutorial discretion has been conscientiously undertaken, the only question for the court is whether the offence has been committed or not.
In Wandsworth LBC v Rashid  EWHC 1844 (Admin),  Env LR 22 the court’s finding that it would have been reasonable for the local authority to take another course of action did not mean prosecution was oppressive or therefore an abuse of process. The local authority was not required to go through each of the other possible courses of action in order to justify its decision that the course of action it had taken was lawful.
It remains open to the prosecution in an individual case, for good reason, to disapply its own policy or guidance (R v A). Even where there has been a breach of a prosecuting authority’s clear and settled policy, the court will only intervene where to allow the proceedings to continue would bring the administration of justice into disrepute: Jones v DPP  EWHC 50 (Admin);  R.T.R. 3, DC.
In R (Barons Pub Co Ltd) v Staines Magistrates Court  EWHC 898 (Admin), in the context of food safety and the statutory code of practice, the local authority’s failure to follow enforcement policy was found insufficient to constitute an abuse of process, the additional element of “oppression” was required in that context. The Court included within oppression a “decision to prosecute … made in circumstances that could be described as entirely arbitrary” (§48).
An example is R v Adaway  EWCA Crim 2831, in which the court found that the prosecution had not given any thought to its prosecution policy: it had effectively been using the criminal courts to resolve a trade descriptions issue which ought to have been resolved in the civil courts or by mediation. The judge made findings at sentence which amounted to the grounds on which he had been asked to stay the case at the outset. The prosecution was oppressive and so ought, exceptionally, to have been stayed for abuse.
In short, regulators must make the decision whether to prosecute rationally; provided they do, they should not be worried about being second-guessed by the courts.
Next week James Puzey, also of St Philips, will write on Proportionality and The Regulator’s Decision to Prosecute in the time of Coronavirus