[2025] EWHC 2684 (KB)

The classic formulation of ‘reasonable and probable cause’ comes from Lord Devlin’s speech in Glinski v McIver [1962] AC 726 (HL) at pp.766-767;

“It means that there must be cause (that is, sufficient grounds; I shall hereafter in my speech not always repeat the adjectives "reasonable" and "probable") for thinking that the plaintiff was probably guilty of the crime imputed: Hicks v. Faulkner. This does not mean that the prosecutor has to believe in the probability of conviction: Dawson v. Vandasseau. The prosecutor has not got to test the full strength of the defence; he is concerned only with the question of whether there is a case fit to be tried. As Dixon J. (as he then was) put it, the prosecutor must believe that "the probability of the accused's guilt is such that upon general grounds of justice a charge against him is warranted": Commonwealth Life Assurance Society Ltd. v. Brain. Perhaps the best language in which to leave the question to the jury is that adopted by Cave J. in Abrath v. North Eastern Railway Co.: "Did [the defendants] honestly believe the case which they laid before the magistrates?"”

Lord Devlin explained in Glinski at p.768:

“The question is a double one: did the prosecutor actually believe and did he reasonably believe that he had cause for prosecution?”

As Lady Hale explained in Williamson -v-Attorney General of Trinidad and Tobago [2014] EWCA Civ 1587

“On the question of reasonable and probable cause, or the lack of it, a prosecutor must have ‘an honest belief in the guilt of the accused based upon a full conviction, founded upon reasonable grounds, of the existence of a state of circumstances, which, assuming them to be true, would reasonably lead any ordinarily prudent and cautious man, placed in the position of the accuser, to the conclusion that the person charged was probably guilty of the crime imputed’: Hicks v Faulkner (1878) 8 QBD 167 , 171 per Hawkins J, approved by the House of Lords in Herniman v Smith [1938] AC 305 , 316 per Lord Atkin. The honest belief required of the prosecutor is a belief not that the accused is guilty as a matter of certainty, but that there is a proper case to lay before the court: Glinski v McIver [1962] AC 726 , 758 per Lord Denning.”

So there is a subjective element and an objective element to the existence of reasonable and probable cause requiring a finding as to the subjective state of mind of the police officer responsible (i.e. no honest belief), and an objective consideration of the adequacy of the evidence (i.e. the circumstances are such that they would lead an ordinary and prudent man to believe in the charge). When assessing this issue it is immaterial to consider what the facts were unless they were, or should have been, in the knowledge of the officer/s concerned at the material time.