If a person believes that information relating to him or her is being unlawfully disclosed, it may be possible for them to rely upon the civil law of confidentiality.

If someone reveals, or attempts to disclose, information relating to an individual's HIV status without that person's consent, and the discloser of the information received it on trust or as part of a contract or agreement with the sero–positive person, then it is likely that a breach of confidence has occurred. In such circumstances the person concerned may be able to get an injunction preventing disclosure and/or awarding damages. They may also be able to get a declaration from the court stating that the information is confidential (see Remedies below).

In law, a duty of confidence arises “whenever the party subject to the duty is in a situation where he knows or ought to know that the other person can reasonably expect his privacy to be respected.” (Campbell v MGN Ltd [2004] 2 AC 457, per Lord Hope of Craighead at para 85).

The law of confidence does not only apply to professional and business relationships: the courts have been willing to protect highly personal information disclosed without authority by spouses and friends. (Argyll v Argyll [1965] 1 All ER 611, Stephens v Avery [1988] 2 All ER 477).

A remedy for breach of confidentiality can exist in contract or equity (i.e. breach of trust). It has also been accepted by the courts that confidential information is a property right (Prince Albert v Strange (1849) 2 De G and Sm 652, 64 ER 293, (on appeal) 1 Mac & G 25, 41 ER 1171). As such the courts are able to protect the person who wishes to keep confidential information from being disclosed, even though there may not be a relationship between the parties which requires confidentiality. Therefore the court can stop a third party from disclosing confidential information they have managed to get hold of.

The law of confidentiality does not provide absolute protection, however, and is subject to three important “limiting principles” (see Attorney-General v Guardian Newspapers Ltd (No. 2) [1990] 1 AC 108, per Lord Goff of Chieveley at 282):

(1) It only applies to information which is actually confidential.  Once information enters the public domain, it is no longer protected by confidentiality.

(2) It does not apply to useless or trivial information.

(3) Although it is in the public interest that confidential information should be protected, that public interest may sometimes be outweighed by another public interest favouring disclosure. In such cases, the public interest in confidentiality must be balanced against the public interest in disclosure.

An example of the third “limiting principle” arose in W v Egdell [1990] 1 All ER 835, where the Court of Appeal accepted that, in that particular case, it was in the public interest for a medical practitioner to disclose details of an individual's health status to a third party. In that instance a consultant had disclosed to the Home Secretary his medical report on a patient who was seeking release from a mental hospital. That medical report suggested that the patient may still have been dangerous and was therefore questioning whether he should be released.

The general principle is however that it is in the public interest to maintain confidentiality. Sometimes there are said to be competing public interests, i.e. the public right to know, as opposed to the public's interest in the maintenance of confidential information. This is best illustrated by the case of X v Y [1988] 2 All ER 648. In that case, a national newspaper sought to disclose the names of two HIV–positive doctors. The Health Authority sought a permanent injunction preventing the paper from publishing the names. The judge in allowing the injunction stated:

“I keep in the forefront of my mind the very important public interest in freedom of the press. And I accept that there is some public interest in knowing that which the defendants seek to publish. But in my judgement those public interests are substantially outweighed when measured against the public interest in relation to loyalty and confidentiality both generally and with particular reference to AIDS patients' hospital records.”

A similar approach was taken in the more recent case of H (A Healthcare Worker) v Associated Newspapers Ltd [2002] EWCA Civ 195, where a dentist who had been diagnosed as HIV-positive was granted an injunction preventing a newspaper from publicly identifying either him or the health authority for which he worked.

It would appear from such cases that there are three principles which justify, in the public interest, the disclosure of confidential information (see Kennedy and Grubb, Medical Law (3^rd edn), Chapter 8, 2000). These are:

• The disclosure is to be made only to those whom it is necessary to tell so as to protect the public interest.
• To justify the disclosure any risk must be real and not fanciful.
• It may be that only a risk involving physical safety of the public justifies disclosure.