Abstract: Sudden cardiac arrest (SCA) is among the three most prominent causes of death in industrialized nations. Therefore, experts are calling for solutions, including smartphone-based systems to mobilize volunteers. German researchers are developing a crisis response system with a crowd tasking app. It aims to help reduce the effects of large-scale events, but also of ad-hoc incidents including SCA. This paper describes an approach to determine the potential of the system to increase the survival rate of SCA illustrated by an example. Its concept was analyzed by five experts from three countries and benefited from their feedback.