On 5 August 2009 at 2.29am, Ms Michael dialled 999 requesting police protection from her historically aggressive ex-boyfriend. Ms Michael told the call handler that her ex-boyfriend had come to the house, found her with another man, bit her ear and had taken the other man away in the car saying he would come back to hit her. Later on in the call, according to the recorded transcript of the conversation, Ms Michael stated her ex-boyfriend had told her “I’m going to drop him home and (inaudible) [fucking kill you]”. The call handler later gave evidence that she had heard “hit you” rather than “kill you”.
Ms Michael lived in the area of South Wales Police, but the call was picked up by a telephone mast in Gwent and rerouted to the Gwent Police call centre. The call was graded by Gwent police as a G1 call, requiring an immediate response by police officers. When giving the South Wales Police an abbreviated version of events, the call handler did not reference the threat to kill and the priority of the call was downgraded to ‘G2’: officers should respond within 60 minutes. A second call was received at 2.43am during which Ms Michael was heard to scream and the line went dead. Police officers arrived at Ms Michael’s home at 2.51am to find she had been brutally attacked and had died from her wounds.
Ms Michael’s family claimed against the two police forces for damages for negligence and under the Human Rights Act 1998, invoking right to life under Article 2 of the ECHR. The police forces sought a strike out of these claims or summary judgment, which was refused at first instance. On appeal, the Court of Appeal reversed that decision in part and held unanimously that there should be summary judgment in favour of the defendants on the negligence claim but the Article 2 ECHR claim should proceed to trial. The claimants appealed to the Supreme Court on the claim that the police were liable in negligence. The respondents cross appealed against the decision to allow the claim under the Article 2 of the ECHR to proceed to trial.
The Supreme Court upheld the Court of Appeal judgment by a majority of 5-2.
While deliberating this case, the Court considered two issues. The first, so-called the “Interveners’ Liability Principle” (because it was brought forward by the interveners Refuge and Liberty), raised the question that if the police are aware or ought reasonably to be aware of a threat to the life or physical safety of an identifiable person, or member of an identifiable small group, do they owe a duty of care to that person under the law of negligence? The second, “Lord Bingham’s Liability Principle” (from Lord Bingham’s dissenting judgement in Smith v Chief Constable of Sussex Police), asks that if the a member of the public gives the police apparently credible evidence that a third party, whose identity and whereabouts are known, presents a specific and imminent threat to his/her life or physical safety, do the police owe a duty of care to take reasonable steps to assess such a threat and prevent it?
The Court referred to a large list of cases in which the courts had previously touched upon whether the police owe a private law duty to a member of the public at risk of violent crime, in addition to their public law duty to prevent violence and disorder. For example, the Court drew attention to Hill v Chief Constable of West Yorkshire, where a claim was brought against the police by the mother of the last victim of a notorious murderer. The claimant alleged the police had made a number of mistakes in their investigation and should have arrested the murderer before he had the opportunity to murder her daughter. It was held that the police were under no liability in negligence and the general duty of the police to enforce the law did not carry with it a private law duty towards individual members of the public. All the case law referenced precluded such a liability under common law.
The Court rejected the Interveners’ Liability Principle as this liability could not be limited to particular potential victims. They gave the example of the police failing through lack of care to catch a criminal before he shoots his intended victim and also a bystander and asked if it’s right one of them is entitled to compensation but not the other. The Court reasoned:
“…the duty of the police for the preservation of the peace is owed to members of the public at large, and does not involve the kind of close or special relationship (“proximity or neighbourhood”) necessary for the imposition of a private duty of care.”.
The Court further argued that police priorities should not be affected by the risk of being sued under negligence  and that the significant financial implications on both the police and the public purse is the only sure consequence of opening up the police force to this risk.. Lastly, the Court rejected the Interveners’ argument that consistency between common law and the Convention should be encouraged and relied upon as ECHR claims have different objectives from civil actions such as negligence.
Lord Bingham’s Liability Principle was rejected for the additional reasons that it would be unsatisfactory to draw dividing lines according to who reports the threat (victim or bystander), whether the threat is credible and imminent or credible but not imminent, whether the whereabouts of the threat-maker are known or unknown, and whether the threat was aimed at person, property or both. The Court also noted that it was for Parliament to determine the existence and scope of such a public compensatory scheme.
Lord Kerr and Lady Hale dissented.
Lord Kerr would have allowed the appeal as there was sufficient proximity to the victim and the police.
“…provided it is fair, just and reasonable that a duty should arise, police will be liable where they have failed to prevent foreseeable injury to an individual which they could have prevented, and there is a sufficient proximity of relationship between them and the injured person.”[Para 149]
He goes on to explain that the necessary proximity is supplied if the police know or ought to know of an imminent threat of death or personal injury to a particular individual which they had the means to prevent.
“In my view, the time has come to recognise the legal duty of the police force to take action to protect a particular individual whose life or safety is, to the knowledge of the police, threatened by someone whose actions the police are able to restrain.”
Lord Kerr also sets out a clear distinction between damage to property and damage to life:
“It is entirely right and principled that the law should accord a greater level of importance to the protection of the lives and physical well-being of individuals than it does to their property.”
Lord Kerr further distinguished the public from the police in applying the general common law principle that members of the public are not required to protect others from third party harm. This protection of autonomy does not extend to the police force whose essential and critical duty it is to provide precisely that type of protection. 
Lady Hale agreed with Lord Kerr’s analysis. In her view the policy reasons said to preclude a duty in a case such as this are diminished by the existence of claims under the HRA and that the police already owe a positive duty of care in public law to protect members of the public from harm caused by third parties.