Abstract: Vulnerability/lethality (V/L) tools used to assess weapons effects in targets often need some kind of rule to assess the status of each vital component being hit. The target functionality on a system level can then be decided, based on the components that are functional as opposed to non-functional (killed). Rules of this kind are often referred to as component kill criteria. Descriptions of criteria and methods of how to assess them are rare in scientific journals, probably due to economic values, classified V/L tools, as well as classified input data to the tools. This paper presents the results from an attempt to define the penetration kill criterion of a relay via simulations. The result is compared with previously published experimental results and the methodology is discussed. Despite some shortcomings in tools and methodology it is believed that simulations can, to a large extent, be a successful way to define kill criteria for components since experimental studies will rarely be feasible due to the cost.