From time to time the courts decide important cases without noticing their broader implications, and thereby set the law off in the wrong direction. Such a case, I fear, is R v. Chargot Ltd. and others [2008] UKHL 73, [2009] 1 W.L.R. 1.

This arose from a fatal accident at a construction site, in which the driver of a dump-truck managed to tip it over and bury himself under the load of soil that it was carrying. This resulted in the prosecution of three persons – two legal and one natural – for offences under the Health and Safety at Work Act 1974. D1, the driver's employer, was prosecuted for failure to perform its duty under section 2, which is “to ensure, so far as is reasonably practicable, the health, safety and welfare at work” of his employees. D2, the contractor in charge of the site, was prosecuted for failure to perform its duty under section 3, which is “to conduct his undertaking in such a way as to ensure, so far as reasonably practicable, that persons not in his employment who may be affected thereby are not thereby exposed to risks to their health and safety”. And D3, a director of D2, was prosecuted under section 37, which says that where a legal person commits an offence against the Act, a director is guilty too if it was committed with his “consent or connivance”, or was attributable to his “neglect”. All three defendants were convicted, and all three appealed.

The question for the House of Lords was this: what exactly does the prosecution have to prove in order to establish, in a case like this, that defendants such as these are criminally liable?

According to the prosecution, the answer to this question should be “very little”. The mere fact of an accident at work raises a presumption that the employer has failed to comply with his duties under sections 2 and 3 of the Act, and he is therefore guilty unless the accident was one that it was not “reasonably practicable” for him to prevent; and because section 40 then says that “it is for the accused to prove” that something was “not reasonably practicable”, on this issue it is the prosecution and not the defendant who gets the benefit of the doubt. So in other words, wherever an industrial accident occurs the employer is guilty unless he can talk his way out of it.

The defence, of course, did not accept this. According to them, the prosecutor in such a case bears an initial burden of identifying, in concrete terms, something that the employer did when he should not have done, or failed to do when he should. As the prosecutor in the present case had not put forward any explanation as to how the accident was caused by the negligent behaviour of any of the defendants, they should all have been acquitted. Insofar as section 40 comes into the picture, they said, this only operates to impose on the defendant an evidential burden, and does not deprive him of the benefit of the doubt. In other words, if defendants in this type of case are legally obliged to show they took due care, this only means they must produce an explanation for the accident that is consistent with due care: which, in order to secure a conviction, the prosecution must then demolish.

In a speech delivered by Lord Hope, in which his colleagues all concurred, the House of Lords accepted the prosecutor's arguments in their entirety. “In cases such as the present, where a person sustains injury at work, the facts will speak for themselves. Prima facie, his employer, or the person by whose undertaking he was liable to be affected, has failed to ensure his health and safety. Otherwise there would have been no accident.” In the light of the purpose of the Act, which Lord Hope identified as “both social and economic”, section 40 must be interpreted as requiring the defendant to prove his innocence. And on the facts D3, the director, was rightly convicted too, because when a company is guilty of an offence under the Act “it will be a relatively short step for the inference to be drawn that there was connivance or neglect on [a director's] part if the circumstances under which the risk arose were under the direction or control of the officer.” Res ipsa loquitur.

All of this would have made perfect sense if the context had been a civil claim, brought by the victim of the accident or his family, in search of compensation. Many well-known civil cases, like Grant v. Australian Knitting Mills [1936] A.C. 85 – the case of the irritant underpants – proceed according to just this type of reasoning. But is it just to apply it in a criminal case?

Criminal liability is not about providing compensation for the innocent: it is about punishing the guilty. The aim of criminal proceedings, in other words, is to inflict a hurt upon someone who is perceived to have done wrong. And this it does. A prosecution in the criminal courts, particularly in the Crown Court as in this case, is stressful and expensive; and the resulting conviction, if it happens, is – and is intended to be – stigmatic and potentially painful. Two of the defendants in the present case, including the director, were fined £75,000, and the director was also ordered to pay £103,000 in costs. And for good measure, Parliament has just added to the potential pain of a conviction for these offences by making them all punishable with imprisonment as well as fines: a fact which Lord Hope mentioned in his speech, but only to say that it did not cause him to alter his conclusions.

The practical effect of this decision is to turn an important group of offences of negligent behaviour into offences of “situational liability”. What is punished is no longer negligent conduct in the running of your business, but the fact of being an employer or director in an organisation where an industrial accident has happened; in which situation, should you find yourself, you are now liable to two years' imprisonment as well as massive fines, unless you can identify an innocent explanation and persuade the court that it is probably the truth.

All this is no doubt deeply satisfying to the tabloid cast of mind, which believes that for every accident there is Somebody To Blame, who must be identified and punished, preferably by putting him in prison. But it takes our criminal law back to the harsh days of the early common law, when criminal liability for causing death was strict, and (as Pollock and Maitland put it) “The man who commits homicide by misadventure or in self-defence deserves but needs a pardon.”