International human rights and humanitarian law stipulate that prisoners have the right to be treated humanely and especially receive adequate medical treatment. However, so called “natural” deaths in custody are frequent and often considered “natural” because (1) there are no external signs of violence; (2) there are other health related reasons that seem obvious; and (3) time, guidelines and material is lacking to advise health care workers or international personnel on the spot how to proceed in such cases. The different partners involved in this research examined the conditions under which deaths in custody should be investigated and prevented. It resulted in the elaboration of practice guidelines which will prepare humanitarian workers for investigations of deaths in custody worldwide.