Police owe a positive obligation under the European Convention on Human Rights to investigate serious crimes against the person, and serious failings of an operational as well as a systemic nature can give rise to a right to compensation, a majority of the UK Supreme Court ruled today.

The case was brought by two victims of John Worboys, the "black cab rapist" in London, whose pending release on parole is now the subject of separate proceedings before the courts. The present appeal, by the Metropolitan Police with the support of the Home Secretary, was against judgments of the High Court and Court of Appeal in 2014 and 2015 upholding claims that police failings in the investigation of Worboys’ offences against the claimants, in 2003 and 2007 respectively, constituted a violation of their rights under article 3 of the Convention, which provides that “No one shall be subjected to torture or to inhuman or degrading treatment or punishment.” The appeal was heard before the Supreme Court last March but judgment was only given today.

The police accepted that both respondents were subjected to serious sexual assault by Worboys, and further that they made significant errors in each of the investigations into the crimes committed against them. However they challenged the rulings of the courts below that a positive obligation to investigate did exist and that, in this case, this obligation had been breached. They argued that the duty of the police to investigate, detect and prosecute crime was of a communal nature and one that was owed to the public at large, not to individual citizens.

All five Justices agreed that the appeal should be dismissed, while differing as to the extent of the duty on the police. Lord Kerr, who gave the main judgment, supported by Lord Neuberger and Lady Hale, held that there was an operational duty to conduct a proper inquiry into behaviour amounting to a breach of article 3; Lord Hughes considered that there was a positive obligation to ensure there were appropriate legal structures in place but that there was no operational obligation. Lord Mance recognised that European jurisprudence had moved beyond the more limited position stated by Lord Hughes, but said that certain “caveats” should be placed on the working of the extended duty.

Lord Kerr reasoned that in order to be an effective deterrent, laws which prohibited conduct constituting a breach of article 3 had to be rigorously enforced, and complaints of such conduct properly investigated. Deficiencies in investigations did not have to be part of a flawed approach of the system generally for a breach of article 3 to arise. It was clear, however, that errors must be serious in order to give rise to such a breach. Although it was argued that there was no clear European jurisprudence to that effect, the case law did demonstrate a clear and constant line of authority to the effect that the state has a duty to conduct an effective investigation into crimes involving serious violence to the individual. It had consistently been held that the positive obligation to investigate effectively was not solely confined to cases of ill-treatment by state agents. The basis of liability was different from that under the common law, which did not recognise a duty of care in this respect.

Lord Neuberger observed in support: "It would not merely be formalistic, but both unjust and unrealistic, to hold that an investigation, which was seriously systematically defective in practice, nonetheless complied with the article 3 investigatory duty simply on the grounds that, while the systemic defects occurred in practice, they did not reflect the systems as laid down officially. Whether the wider or the narrower approach is correct, the court must surely consider the real, not the hypothetical."

For Lord Hughes, the European case law left uncertainty as to the source and extent of the investigative duty. The proper test for the positive obligation under article 3 to investigate reports of past violence was whether the state had a proper structure of legal and policing provision designed to punish it when it occurred and had administered that structure in good faith and with proper regard for the gravity of the behaviour under consideration. In this case as there were plain structural errors.

Lord Mance considered that the distinction between operational and systemic failures had been replaced by a distinction between simple errors/isolated omissions and more serious failings. The positive obligation under article 3 only related to more serious failings. He added: "It is evident from the way the [European] Court explains the assessment of the minimum level of severity that it is not going to be easy to predict where it falls in any individual case.”

Click here to access the judgments.