Democratic Alliance v President of the Republic of South Africa and Others, often known as Simelane, is a 2012 decision of the Constitutional Court of South Africa which expanded rationality review to include an evaluation of the relationship between the procedure by which, executive decisions are taken and the purpose for which the relevant executive power is conferred.

The Democratic Alliance, South Africa's largest opposition party, objected to the appointment on the grounds that Zuma appeared to have ignored various factors which cast doubt on Simelane's integrity and honesty.

Yacoob outlined a three-step test for applying rationality review to executive decision-making processes which ignored certain factors: The first [step] is whether the factors ignored are relevant; the second requires us to consider whether the failure to consider the material concerned (the means) is rationally related to the purpose for which the power was conferred; and the third, which arises only if the answer to the second stage of the enquiry is negative, is whether ignoring relevant facts is of a kind that colours the entire process with irrationality and thus renders the final decision irrational.The court's application of this test to Simelane's appointment was structured by section 9(1)(b) of the National Prosecuting Authority Act, 1998, which held that the National Director of Public Prosecutions must "be a fit and proper person, with due regard to his or her experience, conscientiousness and integrity, to be entrusted with the responsibilities of the office concerned."

The court interpreted this provision as an objective standard for the exercise of the President's constitutional power to appoint a National Director, and found that, in ignoring prima facie indications of Simelane's dishonesty at the Ginwala Commission, the President had acted inconsistently with the purpose with which he had been entrusted, that of appointing a "fit and proper" person to the office.

Acting Justice Raymond Zondo concurred in the substance of Yacoob's judgment but filed a separate opinion to raise a qualification on a minor point.