AT an airfield in Dorset, a vintage aircraft took to the air and then – as too often seems to happen – fell out of it. The fatal consequences led to Rogers v Hoyle [2014] EWCA Civ 257, [2014] 3 W.L.R. 145 – proceedings brought on behalf of the dependants of the deceased passenger, Orlando Rogers, against the pilot, Scott Hoyle, whose negligence they claimed had caused the crash. As required by law, the accident had been officially investigated by the Department of Transport's Air Accident Investigation Department (the AAID). Its report contained findings about the cause of the accident which were helpful to the claimants' case, so they sought to adduce it as evidence. To this the defendant objected and sought to persuade the courts to exclude it. That he failed in his attempt is unsurprising because, as Leggatt J. put it at first instance, “If any non lawyer was told that the law does not permit a court to have regard to the AAIB report when deciding how the accident was caused, I am sure that he or she would express astonishment at the suggestion”. But if the sensible outcome was so obvious, why were lengthy judgments at two levels, with over 70 authorities cited and discussed, needed to produce it?

The arguments for excluding the evidence were two. Reversing the order in which the courts dealt with them, one was that to admit the evidence would be contrary to the public interest – and for this reason the report, even if technically admissible, should be excluded under the generous discretionary powers to control evidence conferred on civil judges by the Civil Procedure Rules. The purpose of an AAID investigation is to uncover, if possible, the true cause or causes of the accident in the hope that lessons can be learnt from it. For this important function to be carried out effectively, witnesses must feel free to open their hearts to the inspectors and inspectors must feel free to present their conclusions without fear or favour. Both would be deterred from speaking plainly, it was said, if pernickety solicitors, bumptious barristers, and censorious judges might pick apart their words and phrases in a later lawsuit. With this in mind, indeed, the Regulations governing marine accidents enquiries had been amended in 2005 to render the reports of the maritime equivalent of the AAID inadmissible as evidence. In the Court of Appeal, the defendant was supported in this argument by the Secretary of State for Transport and by the International Air Transport Association, both of which were given leave to intervene.

This line of argument impressed neither Leggatt J. nor the Court of Appeal. In the nature of things, they said, anyone with information relevant to an accident is a potential witness in later litigation; and, far from increasing the likelihood of his being called to testify at trial, the admissibility of the AAID inspector's report in evidence reduces it, because, if the witness has told the inspector all he knows and this is reproduced in the report, the parties may then dispense with calling him. And there is no good reason, they said, to think that the admissibility of the report would cramp the inspector's style when writing it, because the inspector's task is not to Name the Guilty Man – or indeed to exonerate the innocent one; “… inspectors are professionals who are not in any way concerned with establishing or refuting civil liability” (at para. [89]).

The defendant's principal argument was that, discretion to exclude aside, the report was inadmissible as evidence because of what is called the “rule in Hollington v Hewthorn”.

As older readers will recall, Hollington v Hewthorn [1943] K.B. 587 was the case where, following a road accident, the defendant was convicted by a magistrates' court of careless driving and, in subsequent civil proceedings, his conviction, far from being conclusive of his guilt, was held inadmissible as evidence suggesting it. The Court of Appeal so held because, in their view, the conviction was merely an expression of opinion, and opinion evidence is generally inadmissible. A court would not permit a bystander who had witnessed an accident to tell the court that he thought the defendant was to blame; and, similarly, it should not admit in evidence the opinion of another court to that effect.

The case was vigorously criticised and, on its narrow facts, was long ago reversed by statute. By section 11 of the Civil Evidence Act 1968, a criminal conviction emanating from a UK court is now not merely admissible in civil proceedings, but creates a rebuttable presumption that the convicted person committed the crime alleged; and section 74 of the Police and Criminal Evidence Act 1984 lays down a similar rule for subsequent criminal proceedings. But, in theory, Hollington v Hewthorn is still authority for the wider proposition underlying it and, like a ghost, it periodically rises from its grave to haunt litigants who, like the claimants in the present case, wish to adduce in evidence the findings of other courts or of investigative bodies like the AAID.

Where this happens, the courts usually contrive to find a way to circumvent the rule if they feel the merits so require, as indeed they did in the present case. Though opinion evidence is generally inadmissible, the courts will of course receive opinion evidence from experts who know about technical topics which fall outside the court's own areas of expertise. The report of the AAID inspectors, said the judges in this case, was admissible because the inspectors were experts, able to deploy skill and knowledge that in the court itself was lacking. So, although the rule in Hollington v Hewthorn applies to findings of courts and tribunals, it does not apply to findings made by investigators who have special skills. Thus, in the end, and as usual, common sense prevailed.

However, that it usually prevails does not mean that the law in this area is satisfactory. First, when common sense does prevail, it often does so only after long and costly legal argument and the expenditure of valuable judicial time. And, secondly, common sense does not invariably prevail. The rule in Hollington v Hewthorn is still occasionally applied and, when it is, it usually produces consequences that seem inconvenient and unjust. In Conlon v Simms [2006] EWCA Civ 1749, [2008] 1 W.L.R. 484, for example, the Solicitors' Disciplinary Tribunal, after a hearing lasting 14 days, concluded that a solicitor had acted dishonestly and struck him off the roll – findings which were then endorsed by the Administrative Court on appeal. But, when civil proceedings were later brought against the solicitor to which his alleged fraud was relevant, it was held that, because of the rule in Hollington v Hewthorn, the findings of the Disciplinary Tribunal were inadmissible. The consequence, of course, was that to prove the fraud it would be necessary to stage a re-run of the proceedings before the Disciplinary Tribunal.

The rule in Hollington v Hewthorn, surely, is a legal nonsense and ought to be abolished. The analogy it is based upon is false, because the finding of a public body charged with investigating or decision-making is not the same thing as the casual opinion of the man on the Clapham omnibus – or the bystander who happened to see it run him over. More often than not, the public body will have examined the evidence when it was fresher, and assessed it with an expert eye. So admitting its findings is likely to make judicial fact-finding more accurate and, usually, quicker and cheaper too. In civil proceedings, at least, the findings of any public body of this sort should surely be admissible in evidence, though subject to the discretionary power of the court to exclude them if persuaded that their admission would not carry the advantages described. And this reform should be achieved not by legislation that further nibbles at the edges of the rule, but by a simple statutory provision that abolishes it full-frontally by name – as when, in 1925, with section 131 of the Law of Property Act, “the rule of law known as the Rule in Shelley's case” was formally abolished.