In the late 1970s and up to 1981 a series of particularly unpleasant sex attacks and murders took place in Yorkshire England. A total of 13 women were killed and seven others survived attack.
Due to his mode of operation the attacker became known as the Yorkshire Ripper. After a huge, although incompetent, man hunt the perpetrator, Peter Sutcliffe was (re-)arrested by chance.
The last of the women to be murdered was a 20 year old student, Jacqueline Hill.
Her mother brought an action against the police, alleging negligence, and said if they had performed as they should have done then her daughter would have been alive. This eventually found its way to the (then) House of Lords which gave judgement in Hill v. Chief Constable of West Yorkshire AC53 which was construed as holding that the police had a general immunity from suit in respect of anything done by them in the course of investigating or preventing crime. In other words, they did not owe a duty of care, in the absence of special circumstances, to protect the public from harm through the (non)performance of their function of investigating crime.
There the matter rested until the 8th February 2018 when the (now) Supreme Court of the UK gave judgement in Robinson v. Chief Constable of West Yorkshire Police.
Mrs. Robinson, a lady of 76, walked past a man, who turned out to be a drug dealer, who was immediately tackled by two other men, who were police drug squad officers.
In the attempt to arrest the drug dealer Mrs. Robinson was knocked to the ground. In consequence she was injured and brought a claim for personal injuries.
The Supreme Court held that Mrs. Robinson’s case involved an application of established principles of the law of negligence. They held that the decision in Hill was not authority for the proposition that the police enjoy a general immunity from suit in respect of anything (not) done by them in the cause of investigating or preventing crime.
The effect of Hill was that the police did not owe a duty of care, in the absence of special circumstances, to protect the public from harm through the performance of their function of investigating crime. However that did not prevent the police from being generally under a duty of care to avoid causing personal injury where such a duty would arise according to ordinary principles of the law of negligence.
In the case of Mrs. Robinson there was a positive act by the police, not an omission, and as such there was a duty of care on the officers at the time effecting arrest.
However the Robinson decision did not affect the decision in Hill as to the (lack of a) duty of care upon the police to properly investigate crime, with the view to preventing other people being injured (or worse) by the perpetrator. To that extent Hill remains good law.
Eleven days after the decision in Robinson, the Supreme Court handed down its decision in Commissioner of Police of the Metroplis v. DSD  UK SC11.
This case arose out of the activities of a man, John Worboys, otherwise known as the black cab rapist, who was eventually convicted of 19 counts of sexual assault, including rape, between 2003 and 2011.
DSD was one of the later victims. She brought proceedings against the police, alleging failure to conduct effective investigations into Worboys (previous) crimes. She alleged that the failures constituted a violation of her rights under Article 3 of the European Convention on Human Rights (‘ECHR’) which provides no one shall be subject to torture or inhuman or degrading treatment or punishment.
The case was defended as to the extent to which there was a positive obligation on states (here represented by the police) effectively to investigate reported crimes perpetrated by private individuals. At both first instance and at the Court of Appeal it was held there was a positive obligation to investigate and that in this case the obligation had been breached, with compensation being awarded to DSD.
An appeal was brought to the Supreme Court which was not successful. The Supreme Court held that to be an effective deterrent laws which prohibit conduct (constituting a breach of Article 3) must be rigorously enforced and that serial failures to investigate will be sufficient to establish a claim.
Thus English law finds itself in the position of having decided or confirmed, in the same month, that a police force’s serial failures to effectively investigate a stream of crimes, that proved to be committed by the same person, does not give rise to a duty of care, and therefore not negligent, and yet does give rise to a violation of human rights.
In Hong Kong, Hill appears to be accepted as good law. The writer is not aware of any actions successfully brought against the police for failure to competently investigate. The extent to which, post 1997, the courts might be willing to adopt the reasoning in Robinson is for the future. There is no direct equivalent in Hong Kong law to Article 3 of the ECHR although analogous provisions might be used by lawyers in the future.