This dissertation is the first monography - as far as can be seen - to concentrate on the specific legal requirements of the mutual resolution concerning complicity. That’s astonishing, since the mutual resolution is the basis of contributing a second person’s act. Therefore, the dissertation firstly examines the base of the mutual contribution of acts concerning complicity. This base is supported by related fields of study. The dissertation develops a foundation model, which allows to establish the precise legal requirements of the mutual resolution of complicity, with respect of form, content and time.