Survival rates for sudden cardiac death treated with external defibrillation are estimated to be up to five times greater compared to cardio-pulmonary resuscitation alone. Computational modeling can be used to investigate the relationship between patch location and defibrillation efficacy. However, credibility of model predictions is unclear. The aims of this paper are to (1) assess credibility of a commonly used computational approach for predicting impact of patch relocation on defibrillation efficacy; and (2) provide a concrete biomedical example of a model validation study with supporting applicability analysis, to systematically assess the relevance of the validation study for a proposed model context of use (COU). An electrostatic heart and torso computational model was developed. Simulations were compared against experimental recordings from a swine subject with external patches and multiple body surface and intracardiac recording electrodes. The applicability of this swine validation study to the human COU was assessed using an applicability analysis framework. Knowledge gaps identified by the applicability analysis were addressed using sensitivity analyses. In the swine validation study, quantitative agreement (R2 = 0.85) was observed between predicted and observed potentials at both surface and intracardiac electrodes using a left-right patch placement. Applicability analysis identified uncertainty in tissue conductivities as one of the main potential sources of unreliability; however, a sensitivity the analysis demonstrated that uncertainty in conductivity parameters had relatively little impact on model predictions (less than 10% relative change for twofold conductivity changes). We believe the results support pursuing human simulations further to evaluate impact of patch relocation.