The cause of the polarized debate surrounding the principle of nemo tenetur lies in the continuing disagreement over its rationale. The principle is not merely a derivative of human dignity; as a constituent guarantee of Article 6(1) ECHR it also safeguards the individual' s autonomous participation in the proceedings. The person concerned must be free to determine their procedural conduct - including their procedural contributions. In this procedural protective dimension, the principle constitutes an indispensable condition for the legitimacy of punitive measures. This procedural power extends to all evidence under the control of the person concerned. The principle of nemo tenetur protects the individual as a bearer of knowledge. As a procedural principle, it applies equally to undertakings. In practice, its protection is effective for undertakings only if all employees are able to invoke it. However, only knowledge acquired in the course of business operations is protected. The principle is infringed by any form of pressure to cooperate, including incentives unrelated to punitive purposes. It applies absolutely; its protective purpose is incompatible with any balancing exercise. German and EU antitrust procedural law do not do justice to the principle of nemo tenetur. The protection afforded to undertakings, which is designed merely as a freedom from confession, falls short of the level of protection required. In addition, there are deficiencies in the concrete design of procedural safeguards, in particular with regard to the use of non-prosecution agreements. The incentive effects of leniency and settlement regimes likewise give rise to conflicts with the principle of nemo tenetur.