After an accident such as Hatfield, prosecutors come under pressure to launch a case. But too often they go ahead without having a leg to stand on

I recently wrote about a conviction for manslaughter that had been overturned by the Court of Appeal (8 July).

News of the record £13.5m fines imposed on Balfour Beatty and Network Rail for health and safety offences arising out of the Hatfield rail accident has eclipsed the earlier acquittal of five middle-ranking managers on similar charges. They had previously been acquitted of manslaughter charges on the direction of the judge. We can only speculate as to the reasons for the acquittals since the criminal courts, unlike civil courts, do not produce reasoned judgments.

Notwithstanding the heavy fines imposed on the companies, the collapse of most of the case does raise the question of why such cases are either started or continued by prosecutors when there seems to be little prospect of obtaining a conviction.

Public prosecutors (whether from the Crown Prosecution Service or the Health and Safety Executive) are subject to a code that sets out a two-stage test for deciding whether to prosecute. First, there is an evidential test under which the prosecutor must consider whether there is sufficient evidence to provide a realistic prospect of conviction. This means evidence that would make a jury or magistrates, properly directed as to the law, more likely than not to convict the defendant.

Second, and provided that the evidential test is passed, there is a public interest test. A prosecution should only be started if it is regarded as being in the public interest to do so. In applying the public interest test, the Health and Safety Commission, in its enforcement policy statement, has said enforcing authorities should usually prosecute where there has been a death resulting from breach of health and safety legislation.

Although a prosecution should never commence unless the evidential test has first been satisfied, it may be that prosecutors are tempted to stand the tests on their head and launch prosecutions after fatal accidents when the evidence is borderline.

Although prosecutors act independently, it would be naive to assume that they are immune to outside pressure

Although prosecutors act independently when deciding whether to prosecute – and in major cases are likely to have the benefit of advice from independent counsel – it would be naive to assume they are immune to outside pressure. After a high-profile incident such as the Hatfield disaster, there is public pressure for the individuals and organisations concerned to answer for their actions, and it would be surprising if prosecutors did not take account of that pressure when deciding whether to start a prosecution. An individual prosecutor charged with the responsibility of deciding whether to prosecute might be inclined to let a weak case go forward.

Once a court case has been started, the prosecution is under a continuing duty to keep the matter under review and, if circumstances warrant it, to call a halt. However, that rarely happens in practice, perhaps because prosecutors are reluctant to take responsibility for stopping a case and would prefer to let the court decide the outcome.

My firm has recently acted for construction industry defendants in two separate prosecutions following fatalities. Both were weak, and in both cases the judge accepted our submission of “no case to answer” – that is, he did not consider that the evidence was sufficiently strong even for it to be put to the jury.

However, in each case, the dismissals came during the course of the trial, several years after the prosecutions had begun and after the defendants had incurred considerable costs in defending themselves (most of the money will be recovered from the public purse).

If the judge recognised that no reasonable jury could convict on the strength of the prosecution evidence, surely the prosecutor should have been prepared to come to a similar conclusion and discontinue the matter before trial. Unfortunately, it seems that high-profile cases too often assume a life of their own and it takes a brave prosecutor to halt the juggernaut.