In common law jurisdictions, the duty of confidentiality obliges solicitors (or attorneys) to respect the confidentiality of their clients' affairs. Information that solicitors obtain about their clients' affairs may be confidential, and must not be used for the benefit of persons not authorized by the client. Confidentiality is a prerequisite for legal professional privilege to hold.
The duty and its source
The lawyer-client relationship has historically been characterised as one of confidence. This duty also constitutes part of the broader foundation for lawyer's fiduciary duties to their clients.
Rationales for the duty
The maintenance of full and frank disclosure between lawyers and their clients is the main justification for the duty of confidentiality. The basis for this rationale is utilitarianism, in that it works to promote the work of solicitors, who are officers of the court. It allows clients to freely discuss intimate details without fear that such information could be subsequently disclosed to the general public. In turn, public confidence in lawyers and the legal system is maintained and promoted. Further, the duty of confidentiality is a constant reminder to lawyers of the loyalty they owe to their clients.
Another rationale is to protect the human dignity of the client.
In criminal cases, confidentiality is also justified to prevent the use of tricked confessions or admissions.
Source of the duty
The duty is sourced from a combination of contract law and equity arising from the distinctive relationship between lawyer and client. The solicitor or attorney is an agent of the client under the law of agency. In contract, the duty arises from terms contained in the retainer agreement. Complementarily, equity prohibits unauthorised use or disclosure of confidential information. In most jurisdictions, the duty is codified in the terms of legal professional rules, such as the Model Code of Professional Responsibility.
Although the duty of confidentiality and fiduciary duties have common origins, they cannot be equated as not all fiduciary duties attract duties of confidentiality and vice versa.
Scope of the duty
In contract
As the lawyer-client duty of confidentiality is primarily sourced in contract law, the wording of implied terms in the retainer agreement determines its scope of operation. Despite its importance, there have been few judicial attempts to resolve the extent of the implied term.
In equity
In equity, protection is attached to information that is capable of meeting the test of confidentiality - whether the information was already public knowledge and whether its communication was for a limited purpose. While this test may indicate a more limited scope of confidentiality under equity, by requiring information to be deemed confidential before falling under the scope, on another level equity may secure a broader temporal protection for confidential information. The duty under contract expires on termination of the legal retainer, whereas the duty under equity remains intact until the information is no longer confidential, which may occur long after the expiration of the contractual retainer.
In professional rules
Legal professional rules have tended to adopt the broad view of the scope of duty recognised in contract law. The obligation to retain information in confidence, according to the professional rules in Australian jurisdictions is premised on its connection with the legal retainer rather than the source of the information. Hence, the professional rules seem to imply that information gained in connection with the legal retainer is deemed confidential. However, though the rules emphasise the importance of the duty of confidentiality, this is not a hard rule. Not all information connected with the retainer meets the legal test of confidentiality. The duty of confidence applies to "any information, which is confidential to a client and acquired by [a] practitioner or [a] practitioner's firm during the client's engagement." For barristers, it is "confidential information obtained by [a] barrister concerning any person."