It is a question that could as easily be found in an ethics examination paper as in a court judgement: should a healthcare professional ever override patient confidentiality in order to protect an innocent third party?
The anonymised claimant in ABC v St George's Healthcare NHS Trust  EWHC 445 (QB) brought a claim against three defendants for not breaching her father's confidentiality and informing her of a serious condition that she was at risk of having inherited and which she might pass on to her own child. Her father killed her mother and was subject to a hospital order. Later he was diagnosed with Huntington's disease, a progressive disorder which is hereditary. He was being treated by the First Defendant. Meanwhile the Claimant was participating in family therapy sessions through the Second Defendant. Both Defendants became aware that she was pregnant just at the time that her father's diagnosis was being made. Her father expressly informed his treating clinicians that he did not want either of his daughters to be told of his diagnosis. Patient confidentiality was respected. Sadly ABC was later diagnosed with the disease. She told the court that although she loved her daughter she would not have chosen to continue the pregnancy had she known of the diagnosis and the risk of it being passed on not only to her but also to her own daughter. The question for the court was whether the Defendants, or either of them were liable in negligence or under the Human Rights Act 1998 for breach of Article 8 of the ECHR.
This case reached the Court of Appeal in 2017 - see Judgments 2017, case 15 where it was determined that the Defendants did have a case to answer and the Claimant's case should not be struck out.
Now Mrs Justice Yip has decided the case on the evidence. Although the principles involved in the case are broad, the Judge emphasises the importance of the detailed facts of the case in her judgment. She also sought to give separate consideration to each defendant, because the facts of the case showed that they were in different situations. For example, she found that ABC was a patient of the Second Defendant, but not of the First Defendant.
The Judge then carefully considered the basic questions of whether either or both Defendants owed a duty of care to ABC and if so what was the scope of that duty, and was it breached.
Yip J found that D1 did not owe a duty of care to ABC - there was no clinician/patient relationship because ABC was not D1's patient,; there was not a sufficiently close, proximal relationship between them to give rise to a more general duty of care; and D1 had not assumed responsibility for ABC. Importantly, however, the Judge did not at all rule out that an NHS Trust, or a clinician, could owe a duty of care to someone who was not their patient.
"I conclude that the courts have been willing to recognise that a doctor or health authority may owe a duty of care to persons other than their primary patient but that such a duty is only capable of arising where there is a close proximal relationship between the claimant and defendant."
In relation to D2, with whom ABC was involved in family therapy, the Judge found that D2 had not "assumed responsibility". She also held that the scope of the duty of care could not be extended wide enough to say that there was a duty of care on D2 to ABC in the context of her status as its patient.
"The duty owed to the claimant in the context of family therapy was quite simply to conduct the therapy with reasonable professional skill and care."
"I find that the breach that is alleged cannot fall within the scope of the duty owed to the claimant as a patient of the family therapy team (or as a participant in family therapy)."
Nevertheless, D2 did have a sufficiently close, proximal relationship with ABC, through its work with her in family therapy, and its knowledge of all the circumstances of the case, that it had
"a legal duty to the claimant to balance her interest in being informed of her genetic risk against her father's interest in preserving confidentiality in relation to his diagnosis and the public interest in maintaining medical confidentiality generally.
"The scope of the duty extends not only to conducting the necessary balancing exercise but also to acting in accordance with its outcome. It would be irrational to hold otherwise. If a doctor is under a duty to perform tests, there is no point in those tests being completed but no action being taken in response. The same is true of the balancing exercise."
This duty did not arise because ABC was D2's patient. But it could arise whenever there was a sufficiently proximal relationship between a doctor and another.
On the facts of the case the Judge went on to find that there had been no breach of this duty of care to ABC. There had been no negligence and no breach of Art 8 (which involves effectively the same balancing exercise). The decision whether to override the father's confidentiality was a difficult and nuanced one. There was professional guidance to follow. It was not possible to say that the decision taken not to inform ABC was unjustified, unreasonable or negligent.
An interesting fact recorded in the judgment is that, later, ABC herself chose not to inform her sister of the diagnosis of Hutington's disease, when that sister became pregnant. This demonstrates the difficulty in balancing different interests and factors in such an awful situation. It was also a factor relevant to causation - what decision would ABC have taken about her pregnancy ahd she been informed of her father's diagnosis? Mrs Justice Yip found that, in any event, the Claimant failed to prove causation - namely, that the outcome that she contended justified an award of damages would have been avoided but for the defendants' negligence (if any).
This case should not be read as imposing a duty of healthcare professionals to override patient confidentiality. As Yip J said:
"The duty I have found is not a free-standing duty of disclosure nor is it a broad duty of care owed to all relatives in respect of genetic information. The legal duty recognises and runs parallel to an established professional duty and is to be exercised following the guidance of the GMC and other specialist medical bodies."
And at 
"The legal duty is likely to arise only in limited factual circumstances where there is close proximity between the at-risk person and the medical professionals. Even where such a duty does arise, it seems to me that the circumstances in which it will give rise to a cause of action will be rare, for the following reasons:
i) The standard of care will be measured by reference to the professional guidelines. The guidelines do not mandate a particular outcome. Further, they take a conservative position. Non-disclosure is the default position and the bar for breaching confidentiality is relatively high.
ii) A decision supported by a responsible body of medical opinion will not be considered negligent even though others may not have reached the same decision.
iii) The courts will recognise the pressures of day-to-day clinical practice and will afford considerable latitude to clinicians taking difficult decisions in that context."
The second point here has echos of Bolam. In cases of a patient's consent to treatment Montgomery will apply. This was not a case of consent to treatment. Rather, it has to be thought of as a duty to a non-patient, that will arise only in narrow circumstances, and which is not a duty to inform, but rather a duty to weigh potentially competing interests, and act accordingly.
The case is not authority for there being a duty on geneticists or others to trawl for near or distant relatives of a patient in order to give them advice. Clinicians are not expected to create a relationship of proximity with a non-patient. But where there is already a sufficiently proximal relationship then they ought to consider the balancing act described by Mrs Justice Yip, or a similar balancing of interests that might require to be addressed in different situations.
Nevertheless, there may be circumstances in which a duty to inform a non-patient does arise, notwithstanding the contrary wishes of the patient. Suppose a decision is made to override patient confidentiality, with harmful consequences to the patient. Would the patient then have a potential cause of action?
The judgment shows that there are few absolute rules in ethics or in tort law. There are nearly always exceptions to general rules. Sweeping generalisations risk trampling over nuance and inconvenient facts. Answers arise when you examine the details. Cases turn on their own facts.